The traditional system is called "hot runner." After the rubber compound is pre-heated in an injection cylinder, it's forced under pressure through an injection nozzle to a network of sprues and runners, finally into the mold cavities. This results in the fastest finished goods production, however, it can also suffer significant material waste because of the scrap created by the runner system. Scrap may be reduced by a “cold runner” injection system at the expense of greater cure cycle times. Injection molds and the specialized equipment needed to run them are costly, so in lower volume situations it is typically more cost effective to use transfer or compression molding techniques.