Model No.HDIA37 Drill Bit Dia. (in.)5/8 Length (in.)1 1/4 Rod Dia. (in.)3/8 TPI16 The Simpson Strong-Tie Hollow Drop-In Anchor (HDIA) is an internally threaded, flush-mount expansion anchor for use in hollow materials such as CMU and hollow-core plank, as well as in solid base materials such as brick, normal-weight and lightweight concrete. Key Features Suitable for suspending conduit, cable trays, pipe supports, fire sprinklers and suspended lighting into concrete Expansion design allows HDIA to anchor into CMU, hollow-core plank, brick, normal-weight concrete and lightweight concrete Internally threaded anchor allows for easy bolt removal Material Die-cast Zamac 3 alloy shell with carbon-steel cone or 304 stainless-steel cone