The commercial availability of SiC-based devices has been limited by a number of factors including wafer supply, cost, wafer size and crystal quality. Recently a number of vendors of 4H and 6H SiC wafers have emerged and 100 mm diameter wafers are commercially available. All vendors now claim to meet or exceed the existing SEMI specifications M55-0304. Both SEMI and manufacturers’ specifications focus on wafer dimensions and gross physical defects such as micropipes that are visible by optical inspection. In this paper we describe high-density XRD and PL mapping measurements on a series of nominally identical, semi-insulating 4H wafers from a range of manufacturers. We show very large variations in crystal quality, polytypism and doping/contamination within-wafer, from wafer-to-wafer and vendor-to-vendor. It is logical to assume that these variations may be responsible for observed variations in device properties and yield.