XS Scuba Tank Holder System XS Scuba Tank Holder TR120 (Single) XS Scuba Tank Holder, 120: Designed to Secure 7.25" (18.4cm) Diameter Scuba Tanks Range: Works with Cylinders of 6.9" to 8.0" (17.53cm to 20.3cm) Diameters Secure Scuba Cylinders to:Boat GunnelsBack of Pickup TruckIn the Garage