The flightdeck steel bezel is a step up from the cas 3 it takes a black and white dial and trades it for carbon fibre and matt silver numerals the case is a mixture of black pvd and a 316l stainless steel bezel and the 50mm sapphire glass to boot emboldened by its exhibition window and the trademark aero strap the steel bezel is the most rigorous elegance timepiece at u boat also available in 43mm