This Sig Sauer part is an extended long-stroke piston for the MCX Spear. The piston is part of the Spear's gas system, transferring gas energy to cycle the action. Use it as a factory replacement or for service of a high-round-count rifle.
- Brand: Sig Sauer
- Type: extended long-stroke piston
- Fits: Sig MCX Spear
- Listed weight: 0.06 lb
- Part number: 4204140-R
