Always carry out precise measurements in millimeters, preferably using a caliper gauge. The correct size of the cap depends on the outer tube size. Outcome example: 25 mmCustom Ferrules are made of alumina or zirconia ceramics, with inside diameters from 80 microns to 1100 microns, in lengths from 2. 5mm, and with features such as multi-step, countersinks, flats, slots, grooves, and chamfers. Our Alignment Sleeves are manufactured to the highest quality. Please use the diagram to help you measure the a, b, c dimensions of the Rubber Ferrules you require. These ferrules can be mated to patch cables with FC/PC. Kyocera's extrusion molding process creates ferrules with excellent coaxiality, and our precision machining ensures excellent concentricity with precise inner and outer diameters. For standard products, please see the.