Snap Caps are marine grade caps that fit over #6 and #8(metric sizes M3 and M4) screws. Tops are 1/2 inch diameter (actually .52). A wonderful way to cover unsightly screws in visible places. Slide the bottom piece on the screw before insertion, install the screw and snap the cap in place. Protects the screw from rust and corrosion. Comes in a variety of colors! Sold tops and bottoms together by the 100 count.