Masterline Pro Heel StrapMasterline Pro Heel Strap The Masterline Pro Heel Strap is a non stretch neoprene covered heel retainer for trick water skiers. It sits behind the heel to hold the toe strap in position through big toe trick manoeuvres, so the strap doesn't shift under load while you're working hand passes and toe holds. Choose the Pro Heel Strap if you're skiing tricks at a level where toe strap movement is costing you accuracy through the pass.