Cheaper sex dolls are inflatable, using air. These dolls, representing the lowest price-range (less than US$75), are usually made of welded vinyl and bear only a passing resemblance to actual people. They have an artificial and typically crudely designed vagina or penis, but due to their affordability, many users are willing to overlook their shortcomings. They often burst at the seams after a few uses, although they are commonly given as gag gifts and therefore many may not be used at all. In Russia, for some years the Bubble Baba Challenge humorously featured participants river rafting on blowup dolls as a matter of entertainment but in 2013 the race was canceled on "health and safety" grounds.