Designed to be attached to any mask with a standardized thread compliant with standard EN 148/1.Gas filters: A2, A2B2, A2B2E2K2, B2E2 and K2Particles filters: P3Combined filters: A2P2, A2P3, A2B2P3, A2B2E2K2P3, B2E2P3 and K2P3 Special filters: A2B2E2K2HgP3