The knuckle UJ is a universal windsurfing attachment which works with any size rig, although we recommend for our boards using any sail size 5.5m and below. We highly advise going for a knuckle mast base, as due to its design it puts less stress through the board, making it the best one to use for an inflatable windsurfing SUP.
 
Please note: this base is not suitable for 2022 Red Windsurf boards.