Maid-O-Mist Steam Vent 1/2 " Fpt, 3/4 " Mpt Straight The no. 1 steam vent is designed to vent the air from the main lines, as well as on longer runs (depending on building size). 1/2" x 3/4" combination vertical connection.; ; Brand Name: Maid O' Mist Vent Size: 1/2 in. Product Type: Steam Vent Maximum Pressure: 10 psi Features Use one or more at the end of the short main, or the main running to the warm side Use two or three at the end of the long main, or the main running to the cold side Assures even heat distrubution Float prevents water escape Reduces radiator noise USA SHIPPING estimates delivery times and we work to get your item to you as quickly as possible and within those times, but please know it may take slightly longer than the estimate.