automatic sprinkler Features: 1) Nominal diameter (mm):DN20 2) Connect thread: 3/4" 3) Flux coefficient(k):115 automatic sprinklerZSTZ- ... .There are two different nominal diameter, that is,DN 15mm, connect thread R1/2”, flow coefficient 80, rated W.P 1 ... .2MpaDN 20mm, connect thread R3/4”, flow coefficient 115, rated W.P 1 ...