200mm outside-diameter coil former for metal detector construction, with as much material cut away as possible for a lower volume print. Designed for 30 turns of wire with 1mm diameter insulation. Produces a mono coil for prospecting/treasure hunting as described in the Geotech forums (may require registration to view): http://www.geotech1.com/forums/showthread.php?18323-Chance-PI-coil