This is a set of two slide-type spring bars that allow for one-touch removal of watch bands. When the two are placed side by side, they are about 3mm, so I believe the diameter is 1.5mm. Compatible with cases with a lug width of 18mm. Please use with straps that have been processed to accommodate slide-type spring bars. ※ Please note that the images are reused. ※ If you need more than three, please contact me via the question box. I can accommodate you within a certain range, and I will relist the item with the number you specify. Thank you.