A pair of pads lasts around 20 applications, or 10 to 20 hours. If you're treating most days, or more than one person is using the device, single pairs become a recurring errand.

Ten pairs of EconoPads Large covers that. Large suits the lower back, knees, feet and bigger muscle groups. EconoPads have no internal silver grid - that's the Premium range - which makes them the more affordable way to keep a device stocked.

Buying in bulk comes in for less than ten pairs bought separately.