Round bottom with adjustable inner tube and Nylon bushing with FETFE O-Ring. Optional threaded adapters (8746-75 and -78) will allow safe and easy tubing connect-disconnect. Simply attach tubing to serrated end of adapter, then connect adapter via 7506 bushing to inlet and outlet of trap. Serrated end of adapter has six rings; smallest 14mm O.D., largest 16mm O.D. Adapter not supplied with complete unit. Order same 7506 bushing as supplied with trap for use with adapter.