The Benchmade 590BK Boost AXIS Lock Knife Black/Gray Black Plain Edge. Benchmade's new Boost is a AXIS-Assist knife featuring a safety lock design. This new 590 model has a black finished CPM-S30V premium stainless steel blade with a plain cutting edge. Handles are built with dark gray Grivory / Black overmolded Versaflex for strength and increased grip. The Ambidextrous dual thumb studs and a reversible tip-up clip.