PRYDE Futures GL Side Bites Fins 2-fin setSET OF 2 FINS can be used as side bites for longboards, or rear trailer fins for a quad fin setup. For Single Tab fins, longboards usually use the 3 4" base size, while quad trailer fins are usually 1 2" base. Check your fin box depth before ordering. Twin Tab only has one size, and can be used for longboard setup and quad fin setup. Sidebite fins add POWER, DRIVE, and STABILITY to your single fin setup. Or turn your thruster setup into a QUAD setup,