Single Brass Knuckles SFK 01 Hardcoat Anodizing Type 3

Dimensions:
Material - Aerospace Aluminum
Coating - Sand Blasting _ Type III Hard Desert Anodizing
Height - 2 3/64’’ (52 mm)
Width - 1 15/32’’ (37 mm)
Thickness - 43/64" (17 mm)
Finger hole diameter - 1" (25 mm) 
Weight - 2 oz (56 grams)

More similar products you can find here:
best aluminum 1 finger brass knuckles near me in the USA

Special hole allow you to use this product as a Keychain.
You can also thread a 550-type paracord lanyard through the hole.
Nice gift for Him.

EDC Craft Store official website is the best place to buy original EDC-products at manufacturer's price.