That would be a thick shim, you can get a new sight from numeric gun parts http://www.e-gunparts.com/productschem.asp...el=1910zMINI-14 for $6.45.
Was your barrel cut? If not no problem. If yes you may have to drill the barrel slot which keeps the sight pinned in place. Also if your barrel was cut, you may have to take a few thou off the barrel dia for the sight to fit.
Was your barrel cut? If not no problem. If yes you may have to drill the barrel slot which keeps the sight pinned in place. Also if your barrel was cut, you may have to take a few thou off the barrel dia for the sight to fit.