This unique system allows for easy color to color matching of couplers and plugs among standard pneumatic interchanges. It also solves the problem of potential crossing and contaminating of different air lines. By using color to dedicate your different air lines , a lubricated line will never be used for a dry line application as long as your couplers and plugs match. ColorConnex Type D, 7 piece 1/4 in. Body Coupler and Plug Kit, red anodized, (1 each sleeve FNPT & MNPT coupler, 2 each FNPT & 3 each MNPT plug).