Black 

Weighs 283 Grams

will mount onto a BSA Bottom Bracket

Includes two doubled-up polymer upper chain guides.

A guide roller profiled for the chain to run on the inner or outer ring.

This was a Blackspire display demo. It has never been mounted on a bike. It's never had a chain near it. It isn't a scratched up battleworn used one. It's basically new open stock. 

Includes mounting instructions

There is only one left.