I have these custom made for Stellar Kayaks or Surf skis. They are very tight fitting and water resistant but not waterproof. They will cut a pound or more from your boat weight when exchanged for stock rubber covers. I have the Stellar Small round, Stellar Med oval, And the Stellar Large oval. Price is each. Takes about 3 weeks to have made if not in stock. In the pictures I have each stock cover on the scale and also the exo covers for comparison. Your results may vary !