I've thrown this together in a rush in response to a question asked by a new member in the shoutbox. I suddenly realised that we didn't have an extensive comparison between the various types of movements found in reps and it's something that newbies would find useful. Like I said, I've thrown this together in a real hurry, so I'll be grateful for corrections, additions etc. I'll update and correct the post with any useful info and correction that you guys come up with. Common movements used in rep watches Non-chronos (i.e. if the watch has subdials, they will not work in the same way as the gen) 1. 21J/DG2813 (note that despite the "21J" description these movements usually run 23 jewels). This is a generic term used to cover a wide variety of cheap Chinese movements - some are better than others, but as a general rule they are low-beat (21,600vph / 6 'ticks' per second) movements, very cheaply built (from as little as $7 for the whole movement) but generally reliable and easy to live with. Usually automatic, but occasionally hand wind, dependent on the watch. A lot of really nice budget watches come with these fitted and whilst the sweep isn't as smooth as, say, a gen Rolex, they're damned good value for money and can just be thrown away and replaced if they break or need a service. There's also the DG4813 variant, which is high-beat but this has become very difficult to obtain of late, so is not commonly seen. It has largely been replaced by the Z2 (see below) 2. Z2 aka 'high beat 2813' aka various other names (POS in some quarters ). Some have suggested that this is one to avoid, but it's not quite that clear cut. Basically a cheap 28,800vph alternative to the "Asian ETA" movements, these are occasionally swapped into existing models by the factories without informing the dealers. Reliability can be okay - provided you get a good one. The real issue is that there are no parts available, so servicing can be a problem. The Asian ETAs are a much better choice, but these are maybe worth considering if the price is right - just don't be conned into buying high-priced reps with 'em, it ain't worth it. 3. Asian 'clone' ETA (A2824/A2836 & variants): These are literally copies/clones of the equivalent Swiss (ETA) automatic movements. Generally high quality - although not as well built as the Swiss equivalents - but reliable and with parts generally available (which makes servicing an easier proposition than some other movements). High beat (28,800) and great value. Probably the best choice of movement for higher-quality reps as they give the smooth sweep found in most gen watches 4. Swiss ETA (2836/2824 as above): Supposedly the genuine ETA (owned by swatch group) swiss automatic movements. This is a complete lottery. ETA have not been supplying ebauches outside Swatch group for several years now. There are NO new ETA movements in reps any more - only refurbished (usually with Asian parts). On top of that, as anyone who's been in the game for a while should know, factories tell the dealer the spec of the watch they're producing - and the dealers then use that for their sales pitch. That spec often then changes dependent on what parts the factories have available on a particular day - about which they DO NOT inform the dealers. Given that dealers DO NOT take the back off the watch during QC (nor should they), they're as much in the dark about it as you. At best you get a refurbished (i.e. used) movement with asian parts in it. I wouldn't recommend spending extra for ETA in a rep these days - more often than not, you'll be getting an asian clone. 5. Sellita: As mentioned above, supply of ETA movements is getting very difficult as Swatch group are no longer selling ebauches outside their own group of companies. Sellita are another Swiss company who make a very similar range of high-quality movements. We've seen a few reps with "Swiss ETA" being supplied with Sellitas, but they're fairly rare. 6. Rolex 3135 copy (and other Rolex clone movements). This is an Asian clone ETA automatic movement with modified rotor and bridges to make it look more like the real thing. It's not going to convince anybody who knows their Rolex movements and tends to be less reliable than the alternatives (as well as being more expensive!). There are newer versions beginning to appear which are a little more reliable and look closer to the gen, but they are still near impossible to service and generally inferior to the clone ETAs. Rolex have closed casebacks anyhow, so I really don't see the point in paying the extra for what is, effectively, just a higher-priced and less reliable Asian clone movement. There is one notable exception to the above - the Yuki-sourced movement used by JF in their new (as of 2017) high-end subs. This is a proper copy of the Rolex movements (to the extent of being compatible with a lot of gen parts) and is much better quality than the modified Asian ETA-based clones otherwise supplied in reps. A good movement and well worth consideration. 7. Miyota 9015. With the disappearance of gen ETA movements, some reps are now coming with Japanese Miyota-sourced movements. The 9015 is a case in point - a high-beat 28,800vph 25 jewel movement that is an excellent alternative to ETA or clone ETA models mentioned above. Highly reliable and very good quality. Don't hesitate. 8. Miyota 8215. As above, a solid workhorse movement. The only gotcha is that the second hand on these movements tends to stutter a little and is therefore a lot less smooth than the 9015 or, say, an Asian 2836 clone. The amount of stutter is dependent on the weight of the second hand - the heavier/longer the hand, the worse it's going to be. I'd certainly avoid this movement on watches such as Tudors which tend to have "snowflake" hands. Although the 8215 is reliable, for this reason I would tend to think carefully before buying a watch with this movement. 9. Sea-Gull. Sea-Gull are a chinese maker of both movements and watches. Quality is very close to that of the Swiss and Japanese manufacturers and they're generally a very safe buy - they make clones of several well-known movements (such as the 6497) as well as their own designs. The ST2555 has lately been turning up in quite a few reps. As with Miyota, they're a good choice. Don't hesitate. 10. A6497/A6498: An Asian copy of the Unitas 6497 or 6498 movement. Common in Panerai and various others - it's an ultra-reliable yet inexpensive hand wind movement available with or without swan-neck regulator. Note, however, that there are several different grades and some are better built than others. However, they're easy to service and generally bombproof. Either 18,000vph (5 'ticks' per second) or 21600 vph (6 'ticks' per second) but it is hard to tell the difference visually due to the short seconds hand (where fitted). It can come with or without a seconds hand, but usually with. If it has a seconds hand, the 6497 has the seconds hand opposite the crown (i.e. at 9 if the crown is at 3) whereas the 6498 has the seconds 90 degrees to the left of the crown (i.e. at 6 if the crown is at 3). 11. Swiss Unitas 6497/6498: Again, a hand wind movement. They used to be found in some higher-end Panerai reps but that has now ended since ETA quit supplying ebauches outside Swatch Group some years back. 12. Molnija: Not common these days, but DSN and others have used them on occasion - mainly for vintage Panerai models. This is actually a Russian-built descendant of the Cortebert (latterly Rolex) hand-wind pocketwatch movements used by Panerai and others in the 40s-50s. Very high quality but parts can be tricky to obtain. Functionally similar to the 6497 above and generally reliable, but less robust than the 6497. 13. Asian 52010 aka Liaoning SL6601. This movement has started to appear in the IWC 5007 and could, of course, turn up in other reps with similar functions in due course. It supports secs@9, PR @3 plus date. Liaoning are another well-established Chinese maker of movements - quality is generally good, although parts can be difficult to obtain. Should be relatively easy to service and reliability appears to be decent. Then there are a few that don't fit any of the above groups. Movements advertised as "Asian 23J with power reserve" being probably the most common. These can vary from being basic 21J's with an added module for the PR complication to something like Sea Gull's 23J PR movement - the latter being of rather better quality than most other low-beat autos and likely to be long-term reliable. You'll also see 'Asian 35J" movements advertised fairly frequently - which can also be from a range of sources but are often higher-quality generic Chinese movements similar to the Sea-Gull mentioned above - not as good as a normal Asian clone or other mainstream movement and generally low-beat, but can be good value for money in the right rep. One last oddity worth mentioning is the A7750 as described below. This is sometimes used as a regular automatic movement with the chrono complications removed (most often in Panerai autos). In this form it is much less fragile and many of the caveats mentioned elsewhere no longer apply. Likewise you will - even more rarely - find the same non-chrono A7750 with the auto-wind mechanism removed. This essentially removes the fragile parts that can be damaged by hand-winding on the normal version and is, likewise, not subject to most of the caveats noted elsewhere.   Chrono movements: Japan OS chrono (aka Japan Quartz aka a variety of other names): Basically cheap quartz chrono movements (i.e. battery powered). Reliable, great timekeepers, cheap. There's a couple of varieties with different features, but quality is the same. If you can live with a ticking chrono hand (and seconds subdial) rather than the smooth sweep provided by autos, then there's no reason not to buy one of these. Note that there are 'smooth sweep' quartz movements available and they very occasionally show up in reps. They're a bit more expensive than regular quartz, but good quality. The smooth sweep applies to center seconds (i.e. the chrono hand) only, however - not running seconds in a subdial. A7750 (occasionally called Asian Valjoux 7750): The standard automatic chrono movement used in a vast range of replica watches. Usually high-beat (28,800vph), but there is an older low-beat (21,600 vph) variant which still pops up now and again. Occasionally converted to hand-wind and also used in some non-chrono reps. Can be fragile and is difficult to service due to the lack of available spares. When serviced and running properly, however, it's solid and works well. See the separate sticky about caveats as there are problems with some adaptations to this movement: http://www.replica-watches-guide.com/forum...?showtopic=6101 A7753: This is a variant on the A7750 and not a true clone of the Swiss 7753. Its primary difference from the A7750 is that its native position for subdials is 3, 6, 9 as opposed to 6, 9,12 for the 7750. The resulting lack of transfer gearing needed to move the subdials into the more common 3, 6, 9 position reduces the distance between datewheel and dial eliminating the 'sunken datewheel' seen on many reps. These movement also frequently feature a pusher (usually flush) at the 10 position which operates quick-set date. So far it has only made it into a handful of fairly recent models (notably Panerai). In other respects it shares the same strengths and weaknesses with its A7750 sibling, but the lack of transfer gearing does make it a little more robust in some cases. A7751: This is a goodie as it replicates all the functions of the genuine Swiss movement including working moonphase complication. Found in a limited number of reps (notably a couple of Longines and Patek models). Should be treated gently but generally appears to be reliable. Swiss Valjoux 7750: Used to appear in high-priced reps occasionally, but no longer available to the rep makers since ETA quit supplying ebauches to makers outside Swatch Group. Copy Venus (or sometimes inaccurately described as Lemania). Actually a Sea Gull ST19 - fundamentally the same as the original Swiss Venus movement as Sea-Gull bought the original tooling. This is an excellent handwind chrono movement. Very reliable and feels like quality. The most robust chrono movement in reps outside of quartz options. Don't hesitate.