This rugged aluminum and stainless steel unit bolts on with NO modifications and features a full-length Mil-Std 1913 Picatinny rail on top. Now you can mount a modern tactical sight system such as Red-dot/holo sight and LER scopes for example which will give you the fastest target acquisition possible with this proven battle rifle. Yet the mount will not preclude the use of iron sights, or interfere with receiver-mounted scope bases.
It will NOT fit Chinese made barrels or "Loaded" M1A's with their medium-heavy or heavy barrels. All Stainless barrels are "Heavy" barrels, and will not fit.
Big Book Catalog, Issue:70, Page:251