Silverback Airsoft gives an overview of their Advance Piston Head for their SRS/TAC-41 airsoft rifles... "Advance pistons heads are available in 2 versions: for 'AEG' cylinder head (SBA-BPD-01), compatible with SRS & TAC-41, and for 'GBB' cylinder head (SBA-BPD-02), compatible with TAC-41 using a "GBB" hopup.

This piston head features:

• Viton Oring with a ventilated design.
• No airbrake, short, medium & long airbrake options
• POM piston ring
• NBR 80° Oring damper
• Stainless steel CNC construction, for additional piston mass (from 30.2 up to 32.2 grams, instead of 7.6 grams for the original piston head)

SBA-BPH-01 'AEG' advance piston head
SBA-BPH-02 "GBB" advance piston head"