The Alumi-Span dock system uses 4" high "F" shaped anodized aluminum side stringers that hold a variety of different dock materials. Pine, stained cedar, vinyl, faux wood, and anodized aluminum dock sections are available. Standard dock sizes are: 10'X4', 10'X3', 8'X4', 8'X3'. Choose the smaller sizes for even lighter weight.Special dock section sizes can be built up to a 12' length to accommodate the exact width of your boat lift for easy boat canvas removal.