A structural reinforcement for a hollow member comprising a rigid reinforcing member having a shape that substantially conforms to the cross section of the hollow member to be reinforced with an expandable adhesive material over at least a portion of the surface of the structural reinforcement having one or more extensions on its external surface which control and direct the direction in which the adhesive material expands to bond the reinforcing member to the internal surface of the hollow member, some of the extensions also provide improved reinforcement.