Sturmey Archer BSR ball ring
After removing the cones on the non-drive side of the hub, the ball ring is removed using a ball ring spanner which fits into the notches on the ball ring (alternatively a punch can be located in one of the notches and hit with a hammer).
This is the ball ring for the Brompton BSR - Brompton Standard Ratio - Sturmey Archer 3 speed hub / wheel
Used in the following Sturmey Archer hubs:
Brompton Sturmey Archer BSR - standard ratio 3 speed hub
Sturmey Archer ref: HSA584