I've used two of these to mount two Gibraltar SC-LBBT-TP Cymbal Boom Arms on the Millenium Drum Rack. The upright tubes of the rack came with 28mm boom arms, which after nearly three years had started to "drop" the cymbals mid crash. I've used these adapters to convert the 28mm tubes to take the 22mm Gibraltar arms and they do the job perfectly.
Purchased 2 of these, 1 for my Kick drum to mount a single Mapex tom arm which performs perfectly, 2nd to mount on the Pearl Icon Rack, placed in the cymbal arm holder it allows thinner diameter tube arms to sit without rattling around. Great purchase!