The piston itself is 7075 Aluminum for strength and low weight whilst sporting piston teeth. The piston head is a more normal plastic however, keeping wear down throughout cycling.
This is a series of four with the differing factor being the piston teeth count; model D is standard full teeth, model C has one less tooth on the front, B one less again and this specific model (A) yet one more less.
Now, rather then having to perform fiddly work yourself to shave teeth, you can buy this middleweight, high strength piston and simply select what teeth count you need.
For below 230mm inner barrel & Tokyo Marui Version 2/3/6/7 Gearbox
Piston Material: Aluminum 7075
Piston Head Material: Japan PA
Steel Teeth Material: Hard HRC
Feature: The piston has 11 teeth