The Stayput T Lock system is a new style of fastener for attaching fabric to a hard surface. The Cap and Key mount toa #4 eyelet on the cover and remain attached. With a 1/4 turn twist they easily attach to the Base, which can be screwed to a hard surface.T Lock KeyNylon CompositeInstalls to a#4 Eyelet(9.5mm ID) – Max Eyelet Thickness 5mmPart NumberColourSPF-G871WhiteSPF-G871BBlack