Abstract: An inflatable structure 12 has at least two internal webs 18 extending between upper and lower surfaces 20, 22. The webs are angled to create a different profile on the upper surface 20 from that of the lower surface 22 when the structure is inflated. The structure 12 may form part of a lifting device 10 in which a number of such structures are stacked one on top of another so that the profile on the upper surface 20 of each lower structure nests with the profile of the lower surface 22 of an adjacent upper structure. This increases the contacting surface area between adjacent structures, reducing deflection when the stack is subjected to a load. The webs 18 can be arranged to form at least one ridge in one of the upper and lower surfaces and at least one trough in the other of the upper and lower surfaces opposite the ridge.