Convenient set of 4 barrel shims for M4 style rifles These washers will ensure a contour fit between barrel nut and upper receiver, eliminating misalignment and RIS instability.

Included:

• - 0.1mm X1
• - 0.15mm X1
• - 1.5mm X1
• - 2mm X1

Features:

• - Eliminate gap between rail and upper receiver
• - Precisely aligns fastening screws on RIS systems
• - Ensures stability
• - Prevents RIS from angling during installation