Bio-Fireshield Rectorseal Pass-Thru 4" Round Pass-Thru Device Bio Fireshield Pass-Thru Devices are pre-firestopped and are designed to allow electrical, data or communication cables and pipes to penetrate fire-rated floors and walls. They consist of a square or round section steel sleeve which contains intumescent material. When exposed to heat, intumescent materials expand to form a insulating char plug which restricts the spread of flame, toxic gases, smoke and water. Each device is supplied with 2 end plugs which are inserted after the cable or pipe has been installed to reduce smoke leakage. The devices have an excellent "L" air leakage rating The devices can be opened for easy installation, retrofit or removal of cables. The devices are installed using specially designed mounting brackets which clamp onto the device and require no additional attachment to the wall or floor.