Single Knuckleduster SFK 01 Tropics Micarta

Dimensions:
Material - Micarta
Color - Tropical Green
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 oz (30 grams)

More similar products you can find here:
cool micarta 1 finger brass knuckle dusters buy 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.