First is a false bottom specifically designed for Brew In A Bag process. When you use a mesh bag in a pot, whether it's directly fired on a burner or heated electrically, you want to keep the bag off the bottom. Typical homebrew false bottoms have really small holes and cut off the free flow that mesh bags are know for. Another less desirable choice is a steamer rack or tray that is found in kitchen shops, but none of those are stainless steel.
We've redesigned the support structure by using 1/8" thick, 1/2" wide 304SS flat bar that is rolled into a ring and further supported by an X-shaped cross brace. The legs are made of M8 metric bolts and are threaded into NINE nuts that are welded to the underside of the support structure. This modular leg style allows for just about any height you need just by changing out the length of the bolts. This model is a 18.75" diameterversion,
You have the choice of several lengths during purchase, selectable in the drop down menu. Note that if you select "no legs", the screen still has the welded nuts that will accept legs in the future. Without the bolt legs, the screen will sit about 1/4" off the bottom supported by the bottom rolled ring. The heights listed in the drop down refer to how much clearance you will get between the bottom of the pot and the bottom of the FB support structure.
Based on listed specs on popular pots, this 18.75" model should fit:
Bayou 20 and 25g 19.5"
Brew Built 31g 19.5"
SSbrewtech 31g 19.5"
Spike 31g 19.7"
Of course the fit is not tight on every kettle, but as long as the bag doesn't have several inches of slack, it should not get pulled down into spaces smaller than 1/2" or so.