5506-1508 (FCR) Burton Compatible 55 serie FLANGE PIN INSERT, 15 shell, 8 pin FCR Flange Connector Receptacle (5506) Like the BCR, this is a mounted receptacle. It is more expensive since it is machined from a larger block of stainless steel. It is also more difficult to mount since it requires five holes instead of one. However, it is ideal for use with the right angle plug since keyway orientation can be controlled. It is possible to get this receptacle with an extra O-Ring seal mounted on the F surface for an additional piston type seal (available by special order).