Guntec has Folding Iron Sight Set with QD Knobs Gas Block Height that let you have back up sights just in case your main optic fails. They also will work great as primary sights that fold down for a smoother top for easier storage or retrieval from storage.

Specifications and Features:
Guntec AR-15 Folding Iron Sight Set with QD Knobs LIPSIGHTSET
Steel QD Knobs
Folding Mechanism
Gas Block Height
Matching Pair
Lightweight
T6 Aluminum
US Made
Black Finish

Fits:
Flattop Receiver/ Picatinny Rail and with gas block rail