These chainrings are for 5-Bolt, 130BCD cranksets.
The shift ramps and tooth profiles are specific to 39/53 gearing but are NOT unique to our design; They follow the Shimano spec. In other words, you can use our chainrings with other brands, and the shift ramps and tooth profiles will still line up.
You can order a single chainring or as a set. You can also add new BDop Alloy Chainring Bolts for the complete package.