1) HWT type - worm casting the body and cover straight profile toroidal worm reducer above the worm wheel
(2) HWWT type - worm welded body and cover straight profile toroidal worm reducer above the worm wheel
(3) HWB type-worm casting the body and cover straight profile toroidal worm reducer under the worm wheel
(4) HWWB type-worm welded body and cover straight profile toroidal worm reducer under worm gear
