This is a Ruger Sight, model 90414.
The custom-designed Ruger(R) folding Front Sight seamlessly integrates on the Ruger(R) SR-22(R)" the Ruger(R) SR-556(R)" SR-762(R)" and any modern sporting rifle with a same-plane Picatinny rail mounting system. This lightweight" polymer sight is elevation-adjustable; folds flat to make room for optics and is spring-loaded to allow for rapid deployment with the push of a button.
Features:
Back up front sight
Folds flat
Fits picatinny
Elevation adjustable