The sampling in stainless steel is the same as used with the well known thin wall samplers (Osterberg before Moscow, Shelby, etc.). The rotation of the sampling tube is independent of the rods by a ball beating located between the tube and the outer barrel.
This sampler can penetrate stiff to hard and dense soils because the outer friction between the sampling tube and the soil is completely eliminated by both the rotating outer bit and the fluid circulated in the gap. The lower end (cutting end) of the sampling tube protrudes beyond the rotating bit to avoid disturbance in the sample due to the action of both bit and fluid. The minimum extension (spring completely compressed) is preselectable between 1,5 and 4 cm; according to the stiffness of soil to be sampled.