With the exception of admixtures and fly ash, all moulds and materials are discussed in this chapter. None of the factors listed can be considered in isolation since variation in one will often affect another. Mix design for various forms of precast manufacture is dealt with in Chapter 6. The purpose of this chapter is to acquaint the reader with all the starting variables. The background picture will then be fully understood before one proceeds to put these variables into a process, in order to produce a precast concrete product