Harley Shovelhead Style Glide Riser Bases (Drop-In Hex Bolt Type)
New bases with a very clean chrome finish. Construction is likely an aluminum alloy.
This is the Shovelhead style where a hex-style bolt drops into the base, and a nut, washer, and lockwasher set is used to secure at the bottom. In contrast, most late model Evolution and Twin Cams use a threaded stud.
Manufacturing origins is unknown, but very likely an aftermarket item.
053122 A-3 (OS)