This Boat Trailer Roller End Bell is designed to be paired with the 3 3.5 4 inch Blue Polyvinyl Bow Roller for Boat Trailer Winch Post. This is for a single Boat Roller End Cap/Bell in case you have one that needs replacing, if you are creating your own Boat Trailer Bow Roller Kit you would need 2 of these bells though, one for each end. Remember to use a longer Trailer Bolt or Roller Shaft when adding End Caps or Bells to your Rollers. This Bell requires a 1/2 inch Bolt to fit through it's center bore. This is made of the same top quality PVC or Poly Vinyl that our Blue and Yellow Rollers are made from and it won't mark up your boat or dry rot in the sun like rubber does.