Fits Ammco 6900 & 6950 twin cutting heads, which are used on 4000, 4100, 7000, and 7500 brake lathes. Item for sale is (1)Ammco 6977 Twin Cutter Dust Plug. OEM Ammco part, made in the USA! Each cutting head uses (2) of these plugs (the sale is for (1) plug).