assembly 112 u and 112 l includes a mold half similar to the mold halves described above with respect to the first embodiment and a coupler assembly secured to each mold half the coupler assembly secured to the upper mold half is identified as 171 while the coupler assembly secured to the lower mold half is identified as 173 assembly 173 includes four member 176 177 178 and 179 which form a trapezoid wherein opposite members 176 and 178 are parallel and spaced apart a distance equal to the distance between members 123 l and 119 l and where the distance between opposing members 177 and 179 is such that coupler assembly 173 can fit between adjacent spokes 120 u and 122 u and also between opposing members 115 u and 117 u when axially passed therethrough the lower mold half is secured to assembly 173 importantly when assembly 173 is formed with the dimensions indicated assembly 173 can fit between members 120 u 122 u 130 u and 124 u but will be stopped when members 176 and 178 contact members 119 l and 122 l respectively two linking assemblies 180 181 are provided at the ends of member 176 which when member 176 is adjacent member 119 l.