Product review (5 stars): Solid Cast Iron Wok Ring for Stove grates with 4 Legs
This thing worked well for use on my Iwatani 35FW portable butane stove.  I have a round bottom wok and you could "balance" the wok on the Iwatani but it was not very stable.  A traditional wok ring wasn't an option because there was not way to anchor it to the stove.  The Iwatani stove has a grate with 4 legs and the notches on the bottom of this Whirlpool wok ring sit perfectly on them limiting movement.  As another reviewer mentioned the surface of the cast iron in this wok ring is pretty rough, almost like 80-100 grit sand paper.  I used a wire brush wheel in my Dremel tool to smooth the surfaces where the wok touches the ring and also underneath where the ring contacts the grate on the stove.  It only took a couple minutes to remove the abrasiveness from these 8 areas.