The external cap (C) snaps into the base component and evenly tightens the screen, completing the installation. When rescreening, the cap temporarily pops off, allowing a quick and efficient replacement. Made of UV-resistant window grade vinyl. Never needs painting. 8' lengths. All 1-1/2" wide caps. Base attaches to a 2x4 or 4x4 wooden frame. Screen spline rolls into the spline groove. Cap snaps onto base. Screen-Tight recommends fiberglass screen (including sunscreen). No. WCAP18: Type: Cap, Width: 1-1/2", Length: 8', Material: UV-Resistant Window Grade Vinyl, Color: White, Use with Base Component: BASE18, Pkg Qty: 20, Package Type: Box No. BCAP18: Type: Cap, Width: 1-1/2, Length: 8', Material: UV-Resistant Window Grade Vinyl, Color: Beige, Use with Base Component: BASE18, Pkg Qty: 20, Package Type: Box No. BRCAP18: Type: Cap, Width: 1-1/2, Length: 8', Material: UV-Resistant Window Grade Vinyl, Color: Brown, Use with Base Component: BASE18, Pkg Qty: 20, Package Type: Box No. GCAP18: Type: Cap, Width: 1-1/2, Length: 8', Material: UV-Resistant Window Grade Vinyl, Color: Gray, Use with Base Component: BASE18, Pkg Qty: 20, Package Type: Box No. WCAP38: Type: Cap, Width: 3-1/2", Length: 8', Material: UV-Resistant Window Grade Vinyl, Color: White, Use with Base Component: BASE38, Pkg Qty: 20, Package Type: Box No. BCAP38: Type: Cap, Width: 3-1/2", Length: 8', Material: UV-Resistant Window Grade Vinyl, Color: Beige, Use with Base Component: BASE38, Pkg Qty: 10, Package Type: Box No. BRCAP38: Type: Cap, Width: 3-1/2", Length: 8', Material: UV-Resistant Window Grade Vinyl, Color: Brown, Use with Base Component: BASE38, Pkg Qty: 10, Package Type: Box No. GCAP38: Type: Cap, Width: 3-1/2", Length: 8', Material: UV-Resistant Window Grade Vinyl, Color: Gray, Use with Base Component: BASE38, Pkg Qty: 10, Package Type: Box