Plastic is injected into a preformed metal die. These individual square sheets could be preformed and implanted with the desired effect. Sand casting involves the use of hot molten glass poured directly into a preformed mould. The life of the preformed polymer tapes can vary based on the applications. Transverse seams are required to join ends of preformed pans. Addition of preformed Grignard reagent is often used as the initiator. Some models require heating the road surface prior to the placement of the preformed thermoplastics. Metal caps can be either preformed or in some instances, rolled on after application. It binds to preformed alternative pathway C3-convertases. The addition of preformed chlorohydrin to red blood cells can affect permeability as well. More accurate simulations can be preformed by utilizing quarter-point elements around the crack tip. In addition to cuffed or uncuffed, preformed endotracheal tubes are also available. Decay is sealed under preformed (stainless steel) crowns, avoiding injections and drilling. At the same time, a Friedel-Crafts acylation is preformed on benzene with aluminum chloride catalyst. They must have preformed vitamin A in their diet.