If you have the DG-Lab Coyote, a Rimba or a power box using a 2.5mm audio jack to connect lead wires, this Bi-Polar plug will work great.  If you have a PES, E-Stim System, Folsom, ErosTek or other power box, simply get a 3.5mm male adapter with a 2.5mm female on the other end and you will be all set.  Small and comfortable for beginner anal or vaginal use.  Two inch insertable 1/2 inch diameter that tapers to a 3/8 inch neck.  The base is 1-3/8″ in diameter.