While cruising the bargain cave at the local Cabelas I noticed they had speed bear mounts for the Remington 11-87s on clearance. This lead me to wonder what the difference is between the 11-87 and the 870s to warrant a different mount.
Pretty sure 12ga 1187 is slimmer than the 870. At the receiver that is.
The speed bead mount I bought fit my 11-87 and 870 stocks. Both were the shur-shot stocks about the same size. You have to cut notch's in the stock so the speed bead mount will square up flush between the stock and receiver. Item# 410681. hope this helps!