This front sight is made by Pioneer Gun Works on their own sight base. Its ball shaped, and really reflects the light, which draws your attention to the front sight. It's a lot more rugged than similar sights, and won't break off. Fits standard 3/8” dovetail. May require minor fitting.
The .410 replacemes of Uberti factory octagon barrel front sight on 1873/1866.
The .500 replaces the Marlin factory octagon barrel front sight.