The 6 Canoe Foam Block is a great product when a single replacement is required. Sold in singles. Safe canoe transport requires four blocks.FEATURESEVA foam block provides UV resistance and anti-tear strengthNon-skid bottom for bare roof installationTop cut-out firmly grips the canoe gunnelsUniversal bottom cut-out fits round, square and most factory oval load barsSPECIFICATIONSWeight: .1 lbLength: 6Width: 4.75Height: 3.75