Check the listing for details. TACO 400-4 HY-VENT FLOAT STYLE AUTOMATIC AIR BLEEDER VENT (FAT BOY 1.75" DIAM). Condition: New. Listed at 17.50 USD. TACO 400-4 HY-VENT FLOAT STYLE AUTOMATIC AIR BLEEDER VENT (FAT BOY 1.75" DIAM) PRODUCT DESCRIPTION TACO HY-VENT AUTO-BLEEDER MODEL #400-4 (highest quality) **Very similar to our #416-2 slimline but much FATTER!** 1 3/4" DIAMETER----NOT SLIMLINE #416-2 Install this auto-bleeder on your HYDRONIC SYSTEM to automatically remove the air out of the heating circuit. This unit should be installed at the top port of the 'AIR SCOOP' or at another high point on the system. The thread size is 1/8"-NPT. This is the size on the TOP of the AIR SCOOP. Multiple auto-bleeders may be installed at different points on the loop. You may install one on every circuit (loop). This unit MUST be installed VERTICALLY ONLY! It will not work any other way. These units were bought for HIGH-END INSTALLATIONS and are shipped in individual FACTORY boxes (also suitable for retail sale). © Copyright . All rights reserved.