Like bill1952, I have seen steel ridged conduit that had a Hilti ring at the wall and intumescent caulk filling the ends. The three inch that you mentioned for low voltage cable indicates a bunch of cable. I would question if Hilti caulk could work with a fist size bundle or would it be better to split it up. As it stands with me, I always ask the architect what to use. No architect, then ask the engineer. No engineer, then ask Hilti. Nobody to ask, then the sleeve is steel and reaches 6” past each side of the wall. No sleeve will be larger than 1.5” the caulk will be applied like a gas tight fitting filled with chico. Hilti ring at each penetration.