Grooves on the Bottom. As long as your stove grates have four prongs at 90 degree intervals it will fit, keeps the wok stable so you don't have to worry about it toppling overIt fits stove that has perpendicular style grates, works with different sizes pots/pans with round/Flat base, a round bottom wok. Also fit for a round bottom wok on a gas stove with conventional gratesA rack to stabilize the wok when cooking. It has perfect grooves on the bottom so it doesn't slideAs long as your grates form a cross it will work. It has 4 notches that easily attach to the stove top, good for wok pan, milk pot(bottom diameter more than 3.94inch/10cm)Colour:blackMaterial:cast ironSize:Outer diameter: 21.5cmPackage Contents:1 x Iron Wok RingOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.