inner rubber layer 1 is 0 5 3 0 mm and that of a reinforcing layer 2 is 0 1 0 5 mm and it is further preferred that the interference 5 between the cot and a metal core is between 0 5 and 2 0 mm preferably 0 5 1 0 mm if the thickness of the inner rubber layer is less than 0 5 mm it rather badly interferes with fitting of the rubber cot on the metal core this being thus unadvisable it is also unadvisable to have the thickness of the inner rubber layer more than 3 0 mm for the fitting tightness is then reduced to possibly cause early separation of the rubber cot off the metal core i e early coming off of the rubber cot nor is it advisable to have the thickness of the reinforcing layer less than 0 1 mm for compression on the metal core is then insufficient or more than 0 5 mm for the rubber elasticity of the cot is then affected the thickness of the outer rubber layer 3 is not specifically limited according to the present invention but its proper thickness may be approx 3 30 mm as with ordinary rubber rollers for spinning further for closely fitting the above rubber cot on the metal roller core 4 it is advisable to adjust the interference to 0 5 2 0 mm if it is less than 0 5 mm the rubber.