The ceramic boluses currently in use were seen to vary considerably in terms of dimen-sions (length and width) and mass, as follows (in descending order): 70 mm . 21 mm, 72 g;70 mm . 18 mm, 70 g; 66 mm . 18 mm, 50 g; 58 mm . 12 mm, 20 g. All kinds of ceramic bolus held an inner transponder (32.5 mm . 3.8 mm, 134.2 kHz), according to ISO standard11784.