Unistrut P2072ASQ-EG Electrogalvanized 1/4 Inch Steel Square U Post Base SQUARE MOUNT - 1-5/8" single channel, square mount post base. FOR USE WITH - P1000, P1100, P2000, & P3000 and All 1-5/8" Single Strut Channels. SILVER FINISH - Electro-galvanized; ASTM B633, Type III. THICKNESS - 1/4 (6.4mm); 9/16" diameter hole. DIMENSIONS - 3.8 x 2.1 x 1.5 inches.