Cleaving the fiber tips would be satisfactory for surgery; however, for consistency, the fiber tip ends were instead polished using 0.3-μm-grit aluminum oxide pads (Buehler, Lake Bluff, Illinois). All components were sealed and secured together with a conservative amount of super glue (Loctite, Westlake, Ohio). Only one piece of tubing, the J-groove, needed careful machining to provide a channel for the key, shown in Fig. 4. A 125-μm diameter end mill bit (05EM013-2-070FL, Drill Bit City, Prospect Heights, Illinois) along with a tabletop vertical milling drill (MicroLux, Micro-Mark, Berkeley Heights, New Jersey) were used with micromanipulation stages under magnification to cut the J-groove channel in hypodermic tubing. The design provided a small air gap between the trunk fiber and distal fiber tip, controlled by the length of the locking notch in the J-groove which was 0.3 mm. The distal fiber piece had to remain close to the trunk fiber so that the optical divergence from the trunk fiber did not overfill the fiber tip’s proximal end. The stainless steel cover, originally with a 1.27-mm OD, was filed down to 1.00-mm OD to fit inside a typical flexible ureteroscope working channel with a 1.19-mm ID. The overall insertion distance of the tip was 5 mm followed by a 0.3-mm return after 90-deg. clockwise rotation and release. With the trunk fiber tip barely recessed beyond the J-groove cut and the proximal end of the detachable tip flush with the edge of the locking key, the trunk-to-tip air gap was 0.3 mm, or the length of the locking notch. The detachable tip mechanism that fell above the 200-μm OD trunk fiber, shown in Fig. 5(a) with the tip attached, had an overall length of 10 cm with only 2 cm of that region rigid around the fiber interface, with an overall 1-mm OD. The polyimide tubing and thin steel tubing on the trunk fiber were flexible. The entire detachable system (10-cm length) was manually deflected up to 45 degs. without optical transmission failure, demonstrating that the trunk/tip interface design provided efficient laser beam coupling without misalignment under bending conditions.