04 Ago (2) – 1/2″-20 THIN Hex Nuts (w/Notch, Lock) – Zinc Steel ($1.90/lot) – 0.13″ THK
Only 0.13" thick. They also have a keyed notch which is either for locking action (nuts are a tight fit on the bolt/shaft) or possibly in case clearance/indexing is needed when installing on a shaft, notch is roughly 0.2" wide at the thread end and...