All caps are made of low density polyethylene, and come standard in six distinct colors.  The caps snap over grease fittings to seal out dirt and moisture.  Caps fit standard grease fitting heads, with the exception of flush type, button heads, and pin type fittings.  Caps are available in two sizes/lengths, the short straps have a strap length of  1/8", while the long straps have a strap length of 1".