6 PCS 3/16" Inner Dia. Well Nuts with Screws for Kayak Canoe Small Boats Marine This is a set of durable Well Nuts that are made of rubber and cooper with stainless steel screws. These are suitable for kayak, canoes or boats. It comes in a set of 6 pieces. Dimension of a well nut: 9/16" (H), 1/2" Base Diameter. Well nut's outer diameter: 3/8". Well nut's inner diameter: 3/16".