HT3400 HYDRO GEAR MAINTENANCE & REPAIR

[@dustinw.2608]

That T40 bolt is a "Torx", not a "hex" bolt. Hence the T in T40 for Torx. If it were a hex headed fastener, it would have six sides on the fastener hole in a hexagonal shape, hence "hex" head.

[@dustinw.2608]

Also called an "Allen" head/key, they're the same thing. Just hexagonally driven fasteners. The name Allen just comes from The Allen Manufacturing Co. in the early 1900's making their own brand of hex key and calling it, you guessed it, the "Allen wrench".