of which are positioned inside the loop shaped band material 32 constituting the striking surface the tension bar 34 35 comprises protrusions extending toward the striking surface thus providing a recess 30 behind the band in the striking area 19 thus a slightly flexible striking area is obtained the tension bar is fitted into the milled space 36 being adapted to keep it firmly in place during use connection between the front band with striking surfaces and the back band may be effected by pins 39 or similar protrusions through the tension bar 35 as shown in fig4 f and 4g the physical dimensions of the end pieces 34 and the locking plate 35 are adapted to provide a prefixed tensile tension on the band when being positioned within the loop the tension may be adjusted by exchanging the cassette interchangeable part the locking plate 35 or the end pieces 34 or as an alternative embodiment the length of the tension bar may be adjustable in a per se known way not being essential to this invention the end bottom plate 37 of the putter head locks the interchangeable part 33 into place using locking screws 38 thus the band tension is not easily adjusted or the interchangeable part exchanged during use according to the invention with the version shown the aim is to devise an especially simple barely concealed and relatively uncomplicated club head construction and a relatively simple interchangeable replaceable part cassette which is firmly attached.