Farpoint manufactures two universal "D" sized dovetail bars to fit the metric sized telescope rings. The hole pattern has a 60mm wide spacing at several intervals to fit the William Optics style rings and the many asian made clones. M6 x 1 low head screws are included for mounting your rings to these bars. The bars are available in 178mm & 254mm lengths (7" & 10") As usual the Farpoints fit and finish are as good as can be, with radiused corners and chamfered edges.