I had the drivers side rear slave cylinder blow on me. Got the part home and it looked different. the old one just had the dust seals on the inside and the new one had the seals on the outside. There is a stamped piece steal welded on the backing plate that just touched the boot so I did a bit of looking and found out that their are 2 that could fit my truck. It looks like the difference is 1/16" in the bore size. I got 2 of the 1" sizes (as opposed to the 1 1/16 others) just so they would be the same on both sides. Now the more I think of it the more I'm not sure which one I should have gotten. any help would be great. The truck is a '93 suburban 4x4 and the brake drums are the 11" not the 10".