Like Ex-ki mentioned it's widely regarded as a very reliable 3135 clone that can be swapped into any watch in place of the less reliable SA or SH3135. It accepts most gen parts which is why most people go with a 3135 clone. I'm not sure which gen parts don't fit, as I'm not an expert like some of the guys here, but I recall reading somewhere here that there was some gen part(s) that didn't swap in easily. Maybe one of the experts can chime in. Anyway, my WS swapped in a gen dw and gen reversing wheels with no problem. There's also a good thread here somewhere that one of the experts wrote that goes into the differences between the SH, SA and VR variants in great detail if you really want to drill more deeply into it. You can usually pick one up here or on Ebay pretty easily for $150-180 USD.