The 2100F Soil moisture Probe is a specialized unit designed for investigation of soil suction in small regimes such as near the soil surface, or for laboratory work such as measuring soil suction values at various levels in soil columns. The porous ceramic cup is 0.25" (6 mm) in diameter and 1" (2.5 cm) long and attaches to the tensiometer body via a 6 ft. (1.8 m) length of nylon tubing.