Single Elastomer Bellows Component Seal. With proven CHESTERTON quality, the RBS seal is the ideal choice for sealing small pumps where axial space is limited. Designed with a robust friction drive and large spring format, the RBS provides reliable sealing for a large range of fluids. The RBS seal fits in seal chambers according to EN12756 (L1k) standards as well as chambers with even shorter axial space. It comes with a choice of different mating stationary faces, allowing the RBS to fit in a wide pump population.