One Finger Knuckle Duster SFK 01 Corian Snow White Black Sad Face

Dimensions:
Material - Corian
Finish - Polished
Height - 2 3/64" (52 mm)
Width - 1 15/32" (37 mm)
Thickness - 43/64" (17 mm)
Finger hole diameter - 1" (25 mm)
Weight - 1.6 oz (45 grams)

More similar products you can find here:
the best corian one finger edc knuckles for sale 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 official website is the best place to buy original EDC-products at manufacturer's price.