ProMag Industries ProMag, Rail Cover, Fits Picatinny, 4 Pack PM015A PM015A The polymer panel covers 1913 Picatinny rails" protecting the rail when not in use. The panel cover provides a secure and comfortable gripping surface. The panel is constructed of a proprietary glass-filled" Zytel-based" black polymer. The panel may be custom fit by shortening to cover specific lengths of exposed rails. Package includes four (4) rail panel covers.