In order to ensure that the abutting edges are permanently and securely held together, the abutting edges of at least the outer material layer, preferably of all material layers, have contours which are toothed and complementary relative to each other and inter engage in {HEAD ~ circumferential direction} of {TAIL ~ the hollow cylinder} 
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In order to ensure that the abutting edges are permanently and securely held together , the abutting edges of at least the outer material layer , preferably of all material layers , have contours which are toothed and complementary relative to each other and inter engage in { HEAD ~ circumferential direction } of { TAIL ~ the hollow cylinder }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL