From pswpower
Chainring adapter for bafang bbs01/bbs01b and bbs02/bbs02b. It is suitable for 38T-55T chainring with BCD being 130mm. If the original Bafang chainwheel does not meet your requirement, you can consider buy an extra chain ring and chainring adapter.
Material: #304 stainless steel
Packing list:
1). One chainring adapter
2). 5pcs black stainless steel bolts
Note: The chain ring is not