Three of our safety fins with the screws designed to fit Rock-It Chub (4&';10"), Softy (8&';), and Moby (9&';) boards. This fins are universal with most other screw-through soft top surfboard brands. We have three different sizes--the fins are all 4.5", however the screw length is different between the three sizes to accommodate for thicker boards as the boards are larger. Rock-It Surf screw through fins are more rigid than many competing fin sets, allowing for higher performance and harder/more accurate turns since there is less flex in the fin. All fins are 50/50 foiled.