Aluminium but I dislike the mirror part. It's not easy btonuseninna bike where the steering is lower than yiur body. You will be in the way. Also mirror is magnified and road vibration makes it harder to seeThe arms are to short to give me the right view in the back and are not stable at all.They're looking nice and the mirror it self is fine so I'm keeping them for the general aspect of the bike only and not for being actually practicalmade my bike look real fancy..good solid quality and stylish...easy to fit.I bought blue. The mirrors and brackets are different colours. The brackets wont fit my handlebars or front forks. I wont buy againOK