Beeman/FWB/Weihrauch part.
NOTE: This mainspring is identical to part# BNP-9048 as far as OD and metal strength goes, however, this spring has 31 coils, compared to the R9 (BNP-9048) spring which has 34. As a result, this spring produces a little less energy and it will make the R9 shoot smoother and cock easier.