Each Mortop Aluminum Pulley Wheels is machined from light and strong 7075 AL. Extra machining has lowered the weight to 5.6g per speed wheel. Dirt should accumulate less in the wider holes. There is a little lateral movement to enable a better chain line.
Replace those tired black plastic ones that come with most derailleurs.
Fits most derailleurs. If your current jockey wheel has a hole in the middle and has 11 teeth these should work. Works with 8, 9, 10, 11 etc speed systems.
Tested thoroughly in tough conditions, holding up well.