Excalibur Spider ? Skeleton automatic RD820SQ caliber ? titanium black DLC skeleton case ? 45mm ? Bi?material strap ? white Pirelli edition. Excalibur Spider is the only timepiece on the market to be 100% skeletonized, from the case to the movement. It is Roger Dubuis’emblematic collection with stated sport aesthetic and the famous Astral skeleton signature. AUTOMATIC RD820SQ SERIES: The automatic movement is highlighted by the astral skeleton structure and the micro?rotor, offering a spectacular view on the mechanism. Not only aesthetics, the micro?rotor offers a winding ratio as good as the best single?direction big oscillating weight.