ROSS MUFFL-AIR Pneumatic Silencer 5500A7013, 1-1/4 NPT, Male Thread Aluminum silencer to substantially reduce exhaust noise levels yet produce little back pressure. Product Details In Out Flow Rate 18 Cv Noise Reduction 25 - 25 dB Ports NPT Flow Media Filtered Air Thread Type Male Description MUFFL-AIR Pneumatic Silencer Weights & Dimensions Port Size (In Out) 1-1/4 in Width 2 in Length 5-39/64 in