See for glas tips also http://home.hetnet.nl/~kroese/index.html subpage "insemination" The text is in Dutch. sorry Ik make the tips myself. There are 2 fotos of a coil that i made myself. The wire i use is frame wire stainless steel. Diameter 4 mm. keep the windings compact. 1 cm length. 12v battery charger works perfectly. success H. Kroese Holland.