A composite material blank (190) comprising an elongate blank body (300) extending between a first end face (312a) and a second end face (312b); said blank body (300) extending in a longitudinal direction, parallel to a longitudinal axis thereof, and having four peripheral sides (341, 342, 343, 344); each said first and second end face (312a, 312b) having edges (361a-364a; 361b-364b) which define a trapezoid shape; wherein the peripheral sides (341, 342, 343, 344) of said blank body (190) connect the edges (361a-364a) of said first end face (312a) with the edges (361b-364b) of said second end face (312b); and wherein said first trapezoid end face (312a) is inverted in relation to said second trapezoid end face (312b). A method of manufacturing a composite blank (190), and a wind turbine blade root insert (105) which may be formed from a blank (190).