COMPATIBLE WITH: 2020 or newer iROCKER - BLACKFIN (NOT ULTRA(TM) BOARDS) This single flip-lock side fin is intended to replace lost or broken BLACKFIN paddle board fins. Dimensions: 1 x 5" Please Note: Older boards 2021 and older may not be fully compatible with new replacement fins. If you need to make small adjustments to the length of your fin to achieve optimal fit, we recommend filing the edges of the fin with sandpaper.