Formatt-Hitech 77mm ProStop IRND Long Exposure Kit - Joel Tjintjelaar Signature Edition Contains three densities of the worlds most neutral dark ND filter, the ProStop IRND in 10, 6 and 3 stops. Includes an exclusive long-exposure technique booklet authored by Joel, plus a folding exposure conversion chart. Available in four circular sizes (67mm, 72mm, 77mm, 82mm), 100mm rectangular, and 165mm rectangular. Made in the UK on the most advanced computer-controlled manufacturing equipment in the industry.