The ZX90 Series of Decade Resistance Boxes comprise of 10 instruments to cover a resistance range of up to 1,111,111Ω with instruments available in 4, 5, 6 and 7 Decades. Whilst they are low cost these instruments are of high quality and feature precision low contact resistance switches.

The resistive elements are made of enamelled manganin wire which is non-inductively wound onto high quality formers. Each resistive element is heat treated and undergoes a controlled ageing process to produce the very highest stability and to achieve low temperature coefficient. The instruments are housed in an attractive metal case which is both robust and dust proof.