Hellfire, do you or anyone else know the "operating specs" for the ones used in the DM10X??? Need to buy one to replace the one in my kick!!
To be perfectly honest with you, many people new to the DIY thing get hung up on the whole specs thing about piezo elements. It really isn't that crucial. Any two wire piezo from 20mm up to about 30mm will work just fine. Heck, I've even used 10mm piezo elements in my builds and got then to work just fine.
With Alesis modules I tend not to go above 27mm. That's because the Alesis modules tend to have high input gain on the trigger. They do that because the less expensive triggers tend to use the smaller piezo elements. On the other hand Roland works good with a 35mm piezo, but don't use those on an Alesis module or the trigger will always be too hot. Basically, it will max out too quickly. It won't hurt your module, it will just make it hard to dial in.
Keep in mind these are general rules based on standard type DIY builds. It is possible to use larger piezo elements, but you will need to alter your build to work around the piezo. I hope that helps.