TWICE-AIR A1 LEVEL OF PROTECTION: A1TYPE OF CONNECTOR: thread connector TWICE-AIR A1 P2 R LEVEL OF PROTECTION: A1 P2 RTYPE OF CONNECTOR: thread connector TWICE-AIR B1 LEVEL OF PROTECTION: B1TYPE OF CONNECTOR: thread connector TWICE-AIR E1 LEVEL OF PROTECTION: E1TYPE OF CONNECTOR: thread connector TWICE-AIR K1 LEVEL OF PROTECTION: K1TYPE OF CONNECTOR: thread connector TWICE-AIR ABEK1 LEVEL OF PROTECTION: ABEK1TYPE OF CONNECTOR: thread connector TWICE-AIR ABEK1 P2 R LEVEL OF PROTECTION: ABEK1 P2 RTYPE OF CONNECTOR: thread connector TWICE-AIR ABEK1 P3 R LEVEL OF PROTECTION: ABEK1 P3 RTYPE OF CONNECTOR: thread connector TWICE-AIR P2 R PRE-FILTER LEVEL OF PROTECTION: P2 R (dust-proof performances, only if it is combined with a TWICE-AIR A1 or TWICE-AIR ABEK1 gas filter)