The Stripa Buffer Mass Test involves recording of temperature, water uptake, swelling pressure, and water pressure. The temperature recording is made by use of more than 1200 copper-constantan thermocouples. Swelling, or rather total pressures, are measured by means of about 130 Gloetzl pressure cells, and this system is also applied for recording water pressures in heater holes, back-fill and rock. BAT-piezometers are used as a back-up of the Gloetzl system. The water uptake of the highly compacted bentonite in heater holes and the sand/bentonite backfill that covers the holes is made by 560 electric capacitance gauges. Displacements in the rock that associates the swelling of highly compacted bentonite is measured by applying Kovari's technique.