When I picked up my 4th gen glock 27 I had the shop install nite sights. When I looked at the package I noticed the sight were for a 20,21,29 or39. I have shoot about 300 rounds at the range and I hit the traget dead on as I would with my stock sights. I don't know the difference in the sights between the models. Should I take it back or leave while enough alone?