Hey there, I recently had a chance to test out some new parts that were sent to be by Tienly. From the company that produces some of the best motors money can buy; their piston head!
Now, metal piston heads aren't generally my cup of tea -- however in the current build I'm doing, I'm trying to make it nosier than normal to make things more fun for a CQB gun.
As you can see from the first picture, the piston heads is sporting rather large air ports, at first I was a little bit worried that this would cause air leaks, but after installing everything and testing the compression, I was pleasantly surprised that upon moving forward, the O-ring is very quick to expand, and upon moving backwards, it retracts very nicely as well, meaning that if piston weight wasn't an issue it would act nicely in a high speed build.
One thing that I really like is how they did the bearing side of the piston head. The bearings are of average quality, on par with what you'd expect with your average parts maker, however they include a very nicely machined delrin (or POM?) ring that makes everything sit very nicely inside the piston body.
All in all, I'm pretty happy with this piston head, it's machined nicely, finish is great and the materials feel extremely solid.
I would like to see a POM or delrin version of this piston head made as it would suit my purposes (Japan's laws have the guns locked to 328FPS max, so piston return is limited to a M100 spring) a bit better due to total piston weight.
Average price seems to be about $10-$15 less than the top of the well known "high end" brands.
I give it a "yeah, it's pretty good" rating.