Bore-Up Cylinder for M4A1/XM177/ SIG551/MC51

• Stainless 304 material / 5 types
• Ribbed surface finish increases the cylinder-surface-to-air area to thus increase heat dissipation.
• Fine inner surface finish enhances piston reciprocation.

With a large cavity to produce more air. Stainless steel construction with thin walls and smooth inside finish.