Our risers are designed to fit RecreTec Oar Stands, they are made of UV resistant UHMW. The blocks mount under your oar stand to raise it up 3/4 inch if you need to add height to your oar position. Kit includes 2 blocks with pre-drilled holes, 4 Stainless bolts, nuts and washers for mounting. When a seat with a slide adjustment is added to a Dry Box we use 3 under each Oar stand to obtain the perfect height for rowing with open Oar Locks or Pins and Clips. It is possible with a Pin & Clip set up to only use one and go to a 12" Pin. Now sold each - So many requests we have decided to sell them seperately, without the bolts. Each time you add a riser the bolt size chances. Dimensions: 3/4” thick 5 1/4” wide