Clinical success of fixed prosthodontic procedures is dependent in part upon the dimensional accuracy of elastomeric impression materials and impression procedures. The variable thickness of the impression material in tray may result in dimensional change & inaccuracies in the cast. There is distortion of the impression material during retrieval of stone casts, when multiple casts are poured in the same impression. This book is directed towards the effect of various tray spaces (2mm, 4mm and 6mm) and subsequent repeated pours (2 times) on the accuracy of monophasic polyvinyl siloxane impression material. It was found that the vertical distance of stone dies decreased, whereas horizontal distance increased as the thickness of impression material is increased. There were statistically non significant changes occurring among the repeated pours in 2mm, 4mm and 6mm spaced custom trays.