This is the Apeks Single Tank Adapter Features: The single tank adapter is a great way to quickly attach a single cylinder to a back plate or the WTX harness Made of 316 stainless steel Weighs 1 lb. 1 oz. (490g) without hardware Comes with 2 sets of bolts and one pair of washers and wing nuts 1 bolts for directly mounting to back plate 1.5" bolts for mounting to back plate inside WTX harness The WTX and WTX-D Series is a selection of harnesses, buoyancy cells and accessories which offer unparalleled versatility due to the modular nature of the whole system. Each component can be configured into a highly technical rig for those trained to push the limits, or scaled down to make a travel friendly set up suitable for any diver. The single tank adapter is a great way to quickly attach a single cylinder to a back plate or the WTX Harness."