The waterproof PinPoint chambers have been specially designed for relative beam profile measurements in a motorized water phantom for characterization of LINAC radiation fields where superior spatial resolution is desired. The PinPoint chambers are ideally suited for this purpose with their inner diameters of only 2 mm (model 31014) and 2.9 mm (model 31015/31016). The chamber model 31016 shows a flat angular response, since the measuring volume is approximately spherical. When calibrated against a PTW Farmer chamber, the PinPoint chambers can be used for depth dose and absolute dose measurements. The sensitive volume is vented. The wall material is graphite with a protective acrylic cover.