Many of the practices undertaken to prevent and treat pressure ulcers are contentious, based on estimates and guesses rather than evidence.1 One of the areas of greatest uncertainty, the role of pressure-redistributing support surfaces, has become a common foundation to pressure ulcer care. Since Hibbs2 described an ideal shopping list of support surfaces for a large combined acute and community care provider, special mattresses have been widely disseminated throughout health care services in the UK and beyond.1 This utilisation has not been inexpensive, with 7-8% of all pressure ulcer costs attributed to the acquisition of mattresses.3,4