Tinned cast aluminum base for mounting air terminals to flue tiles. Has two stainless steel bolts for anchoring. 2-1/2 x 2-3/4 in. (6.4 x 7 cm); approximately 11 oz.(312 g). Use suffix 3/8 or 1/2 inch to denote air terminal thread size. Approximately 4 oz. (113 g). Use with 1/2 inch diameter air terminal.