Arnold & Son Watch Nebula 41.5 Steel Rubber 1NEAS.U01A.K002S. Harmonious, radiant and intense, the Nebula’s skeleton movement reveals a structure in grey and blue tones. It combines steel with a PVD treatment on diametrically opposing bridges for a perfectly chic visual effect. In addition to being the most symmetrical of Arnold & Son’s watches, it is ultra-thin, at just 8.73 mm.