Design with elastomer bellows is frequent and among most commonly used NM-1 type has got very good secondary sealing on a shaft with elastomer bellows. This type is highly recommended for sealing media with possibility of crystallization or containing solids in waste water or sewage application. Constructions allow fast and cheap reparation because there is no boned joints. NM-1 seals don’t depend on the direction of shaft rotation. All other metal parts are made of stainless steel.