Finally, there are some special instructions for installing on '67-87 GM Stepsides. On these years the O-ring must be cut to allow it to fit into the curl opening. The adhesive will keep the O-ring in the curl cap groove during installation and prevent the cap from falling out of the bedside curl. Now, your caps are in place, and you are ready to roll. Mar-K's bed cap lights will not only add a nice finishing touch to those bedrails, but also provide a bit more peace of mind by making your classic truck easier to see in low light or complete darkness.