me semble avoir vu ça chez cold steel aussi
chez spartan, ils disent:
All our Bronze (Field) Grade folders incorporate our new “Oil Infused Bronze Bushing System” or “OIBBS”! Our sintered bronze bushings are impregnated with oil which reduces the friction on the blade, thus giving you a tight but smooth blade opening. This system is especially useful for slow speeds, intermittent use, and uneven loads such as are found on folding knives.
chez Reeves c'est un peu similaire