Rigid PMMA flood phantom for the quality control of detector homogeneity and subsequent correction in gamma cameras. The two filling and venting plugs of the Leeds Gamma Flood phantom are situated on the flat surface, not on one of the edges as with many other manufacturers. This is because filling from the edge necessitates that the phantom stands up on the opposite edge. In such an orientation, water pressure develops on the flat faces, forcing them outwards (bulging). The bulging does not easily rectify itself even when the phantom is placed flat, and so the difference in thickness causes unequal thickness of the test solution which might be mistaken for non-uniformity in the distribution of radioactivity. Thickness tolerances on materials and the fillable void are ±1% of nominal ensuring high precision.