ProGrip anti fog insert, been using them for years, i couldn't do without it now.
Anti fog, anti glare at night, has a slight auto tint in sunlight, a great piece of kit.
Beware if you have an Arai lid as it is shaped around the air vents so you need to order one specifically for them, otherwise they're a universal fit.
Wider vision than a pin lock too.
Under £20 on Ebay.