PolarPro Peter McKinnon Series Helix VND 6-9 Stop MagLock Lens Filter SystemMcKinnon Helix VND 6 5 Stop PM 6 9 The 6 9 VND is designed to shoot wide open apertures in extremely bright conditions. The Helix MagLock Filter System was developed both to eliminate the hassle of threading filters on and off, while also providing a filter that's safely locked in place once installed. 6 9 Stops of ND for shooting wide open in bright conditions 5x Faster than threading filters on Magnetic + quarter turn to fully lock down the filter