This Mossberg manufactured black synthetic butt plate is for the model 151M(b) / 151M-B semi-auto rimfire rifle and is in good condition with light dents / wear except for a hole drilled above the magazine tube hole (see photo). This butt plate measures 1 5/16" wide and 4 1/2" tall and may be slightly undersized when compared with your butt stock as they are known to shrink in size over time.