Does buying this once give you a pair or just one disc?
A single rotor, plus 6 bolts.
What material are the rotors made of?
They are made of stainless steel.
How to choose the size of rotor?
You only need to choose the corresponding disc color and specifications.sliver-A:140mm/160mm/180mm/203mm;sliver-B:160mm/180mm;sliver-C:160mm/180mm/203mm;multi-B:160mm/180mm;multi-C:160mm/180mm.
What size is the bolt pattern?
It is 44mm opposite hole pattern.