this is one of a number of things needed for the hyper dimensional resonator said to be 7 layers of 21 awg=21 American wire gauge wire. on a 7 inch long core, I've made a number of them but I used a 8 inch long core and I made pvc spacers to space the coil for the length of 7 inches this way the round spacers makes it very easy to roll wire onto the core , mild steel core was the best and iron core just kept burning out the 3 amp safety fuse , I didn't have soft iron and nothing like the ferrite type cores just some kind of solid looking iron so I have several hdr electromagnets and only 2 are iron types and replacing the 3 amp fuse with higher current rating fuses can fix the burnout problem when useing solid iron bars for the former in an electromagnet , I have 7 layered electromagnets and 7.8 layered in reference to the 7.8hz Schumann resonance, and 7.5 layered in reference to the brain wave frequency, which some may say its 7.8 but who knows for sure and I have found that the hdr can use these various layered electromagnets ok , I've, since I took this picture upgraded the simple electromagnet designs and have handles on them and I used high tempiture polymide tape brought cheap on e bay , cheaper than altronics which also sell them and I used layers of that high tempiture silicon tape over the top , the polymide tape I wrapped one or 2 layers between every layer of coper wound and this makes it very easy to wind the next layer over the top of the previous layers without the coper winds dropping down and making it look uneven and not so level, during testing of my 7.8 layered electromagnet as I got to close to filming it with my digital camcorder , it kept mysteriously shutting down my camcorder so I used a tripod and zoom feature to capture video of 2 watches rotating opposite to each other at the same time in a double field at the one end of the electromagnet, a multipole field north and south at one end