It would be nice to extend knuckles some more, including a set of weaker knuckles that does not boost attack power, but still retains the quicker attack speed.
IMO something like:
Wood Knuckles (+0 Attack, Cooldown 400, 250 durability)
Stone Knuckles (+1 Attack, Cooldown 400, 250 durability)
Bone Knuckles (+1 Attack, Cooldown 350, 300 durability)
Copper Knuckles (+2 Attack, Cooldown 350, 300 durability)
Tin Knuckles (+3 Attack, Cooldown 350, 350 durability)
Bronze Knuckles (+5 Attack, Cooldown 350, 400 durability)
Iron Knuckles (+6 Attack, Cooldown 300, 450 durability)