The 4-arm 104mm BCD (Bolt Circle Diameter) spider mates with virtually all MTB chainrings and those on many city bikes. Only 54 grams, less than 2 ounces.
Now you can trim weight from your bike with alternatives to heavier steel chainring discs, by using your favorite chainring and a new lightweight spider that mates to our freewheels.
The spiders are made from AL 6061-T6, an "aircraft" grade aluminum alloy with high tensile and yield strength and superior resistance to corrosion. At 4.8mm thick they are strong and resilient yet still save well over half the weight of an equivalent size steel chainring disc. They fit onto our flanged crankset freewheels and our chainring adapters.
For some builds you are going to want that steel disc, but for many setups the steel is overkill.