It is housed in a plastic case with 4 mm sockets. This unit include 12 – position switches which select resistance in the range 470 k ohm 220 k Ohm, 100 k Ohm, 47 k Ohm, 22 k Ohm, 10 k Ohm,2.2 k ohm, 4.7 k Ohm, 1 k Ohm, 470 Ohm, 220 Ohm and 100 Ohm.