This TUSA and Scubapro fin strap is the full assembly, including the buckles to fit on the fins, the quick release buckles that clip into the ones on the fin and the rubber strap itself.
The TUSA and Scubapro fin straps use the exact same buckle system, so the strap will fit fins of both brands. Your straps will be branded either TUSA or Scubapro.
These are an essential part of any diver's spares kit, especially when going on trips away! You don't want to miss a dive, because you're not carrying a spare!