My friend is using Nashin 6pot on his F30, never track b4, so far so good on street, price reasonable, at least original product, not sure performance on track or extreme condition.

Let me share with you some experience, I sell BBK few years back when I was active on modding cars, for the refurbished F50, caliper mostly replica, even the factory in China purposely produced it and sell as refurbished to mislead buyer, secondly, what rotor and brake pad they give? I can say mostly Taiwan as I know off, because just the Brembo’s original floating rotor + pads could cost 3-4k, if the seller offer below 5k for the whole package with steel braided and installation, then you must be careful. However, if the rotor/brake are used too, make sure you know how to check how much lifespan left.