Formatt-Hitech 85x85mm (3.35x3.35")Resin ProStop IRND 10 (10 Stops) Hitech filters are made from the highest quality 1.5mm optical resin. the filter is also available in 100mm, 150mm and 165mm sizes. the 85mm size is useable with Hitech 85mm holder systems or any 85mm (3.35-Inch/Size) holder.