21 unworked or semi-worked glass, except building glass; articles made from ceramic, namely, rings, for general industrial and further manufacturing use; Unworked or semi-worked glass, with the exception of structural glass and building glass; semi-finished products made of translucent vitreous glass, namely, tubes not for scientific purposes, glass pipes not for building and not for scientific purposes, bars, figured plate glass, not for building, glass bars in the nature of blocks, unworked or semi-worked glass in the form of rings, none of the foregoing for building purposes; translucent vitreous glass goods, namely, glass tubes not for scientific purposes, pipes not for scientific purposes, bars, figured plate glass, glass bars in the nature of blocks, semi-worked glass in the form of rings, none of the foregoing being for construction or building purposes; synthetic quartz glass, namely, tubes not for building or scientific purposes, pipes not for building or scientific purposes, bars, figured plate glass, glass bars in the form of blocks, semi-worked glass in the form of rings, not for building; synthetic quartz glass fibers, not for textile purposes, not for building; semi-finished products made of synthetic quartz glass, namely, tubes not for building or scientific purposes, pipes not for building or scientific purposes, bars, figured plate glass, glass bars in the form of blocks, semi-worked glass in the form of rings, not for building; synthetic quartz glass fibers, not for textiles purposes not for building; vitreous silica fibers, other than for textile use; synthetic black quartz glass, namely, tubes not for scientific purposes, pipes not for scientific or building purposes, bars, figured plate glass, glass bars in the form of blocks, semi-worked glass in the form of rings, none of the foregoing being for building purposes; semi-finished products made of black quartz glass, namely, tubes not for scientific purposes, bars, figured plate glass, lass bars in the form of blocks, pipes not for scientific or building purposes, semi-worked glass in the form of rings, not for building purposes, quartz glass wool not for insulation purposes; synthetic quartz glass fibres, not for textile purposes, not for building; synthetic opaque quartz glass, namely, tubes not for scientific purposes, pipes not for scientific or building purposes, bars, figured plate glass, bars in the form of blocks, semi-worked glass in the form of rings, none of the foregoing being for building purposes; semi-finished products made of synthetic opaque quartz glass, namely, tubes not for scientific purposes, pipes not for scientific or building purposes, bars, figured plate glass, bars in the form of blocks, semi-worked glass in the form of rings, note for building purposes; synthetic quartz glass fibers, not for textiles purposes, not for building; opaque quartz glass fibers, not for textile purposes; black quartz glass bodies that are opaque throughout, being component parts of lighting systems, namely, lighting installations; semi-finished products made of ceramic, namely, articles made from ceramic, namely, rings, windows, plates, pipes, blocks, for general industrial and further manufacturing use