made of impact and seawater resistant styrene. Reduces the effects of swell and wash on a stationary boat. Quickly fitted and removed. Parts fit inside each other for compact stowage. For 10mm warps, distance 40cm. Diameter: 34cm. Number of Rocker Stoppers required per boat’s length:up to 8m length~3 units8-11m length~4 units11-13m length~5 units13-15m length~8 units15-20m length~12 units(without rope)