The power cylinders and pistons are made from steel. The piston surfaces have brass lining and oil grooves, 1 mm 1 mm with 10 mm spacing. The clearance between piston and bore is approximately 0.02 mm. The displacer cylinder and head is made from a 1 mm thick stainless steel plate and the clearance between them is 2 mm. The displacer also serves as a regenerator, which is made from a
round-hole perforated steel sheet. The stainless steel pot scourer is used as a regenerator matrix.