Not sure what the difference in them is. The purple ones that I've got came in a single poly bush, they don't split, but just put some copper grease on them and they slide in my hand, then there's a metal tube that goes through the middle of it, grease that up too and then with a mallet just tap it in. It'll tighten the bush up to the axle. It's a doddle to fit the bush into the axle, but the job as a whole is an absolute b!tch. I had to remove the rear axle to get a good angle for cutting the old bush casings out. You can remove the axle without disconnecting brake calipers from the brake lines, just manoeuvre them out of the way. Oh and make sure you've got a friend helping you, you need someone to help you lift the axle and hold it there while you screw it all back in.