These heat-shrinkable tubes are extremely flexible, high expansion ratio, do each size of tubing fits a range of busbar sizes. Both BBIT and BPTM tubing are ideal for original equipment assembly, and for retrofit applications where access to one end is available. BPTM (24 kv class) Medium-wall tubing for use on straight or bent bars where some clearance reduction or 25 kv insulation is required. BBIT (36 kv class) Heavy-wall tubing for use on straight or bent bars where maximum clearance reduction or 35 kv insulation is required.