Double Finger Knuckleduster DFK 01 Hardcoat Anodizing Type 3

Dimensions:
Material - Aerospace Aluminum
Coating - Sand Blasting / Hard Desert Anodizing Type III
Height - 2 11/64" (55 mm) 
Width - 2 13/32" (61 mm) 
Thickness - 43/64" (17 mm) 
Finger hole diameter - 1" (25 mm)
Weight - 3 oz / 90 grams

More similar products you can find here:
cool aerospace aluminum 2 finger edc knuckles buy in the USA

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

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