For customers requiring small quantities of parts with very specific properties, a variety of approaches may be employed. One approach is to cast the part using a mold constructed from wood, urethane tooling board or silicone and cast the part with urethane. A gravity cast of a hand-mixed 2-part urethane can be produced that will give a dimensionally accurate prototype. Because of the variety of urethane materials available, desired physical properties can be realized that will mimic the production part.  Inserts can be molded into the part or added afterward.