Small arm to fit the voltage knob on Maplin N93 CX workbench power supply giving greater control when used with model railways.
This item is a also believed to fit the following power supply units with other brand names:
Circuit-Test: PSC-520, PSC-336, and PSC-260
Manson: NRP-2050, NRP-3630, and NRP-6016
Rapid: 85-1901, 85-1902, and 85-1903