The product can be found here:
This is what we mean for TTI Piston Assembly.
when you purchase, will ship all that you see in the above picture. A complete package. You just have to drop it in your HW77.
The Compression tube is coated with hard chrome. It serve the duel purpose.
1) Anti rust
2) Anti friction
The piston also having special anti friction coat in both internally and externally.
Both the parts i.e., Piston and chamber are hardened more than 50 hrc. So rest assured, the parts are ever lasting.
And you will have a stunning beautiful shooter.
Anti-friction ring is purposely not done in the front part of the chamber. The reason is simple. After cocking, the breech hole securing the front part of the chamber well. The back part however required to be steady thus we made the ring there.
Just wanted to show the alignment.
This is how it looks like inside a HW77
A detailed look. The piston and the compression chamber aligned properly with a support from the Synthetic ring.
As said before, the breech hole is securing the front part of the chamber properly as a result you can see the proper alignment thus the gap.
Here is a feedback and video provided by a customer: