Not sure what you mean by ‘they’ but those sleeves are out a older fuel block are 4.70 top and 4.63 at bottom, 4.31 inside. My block bore is 4.530 so if turn them to 4.529, heat the block, chill the sleeve they should drop in. I’ll cut the lip down then make a cutter to cut top of block to accept that lip so it will not move (which I doubt). I think those sleeves are some good material to support a fuel engine. KB sleeves if I remember right. I had vagly thought of using them but after reading the posts they might be the best option plus they where free.