The Gomu from L-style is a new product designed to help prevent the loosening of your shafts from the barrel. The small rubber cap fits over the end of your shaft similar to an o-ring but is small and will prevent the o-ring from bulging out between the barrel and shaft. These are ONE TIME use and a new set must be used if you change or remove your shafts. Sold in a 2 pack. Ideal for Carbon and Metal shafts from all manufactures but will also work on Nylon or Poly Shafts.