Small adjustable spark gap electrodes mounted in a standard 20mm fuse holder. These electrodes are machined from brass so that there are 2mm fins for dissipating heat. These are ideal for small Tesla Coil projects or other low power HV applications. The gap is adjustable from 0 to 10mm apart simply by moving one or both of the electrodes in the holder. Each electrode measures 16mm long, and 5mm diameter.