This is a gear cable stop designed for use on a bamboo, wooden or carbon fibre bicycle where fittings such as these need to be glued and screwed on, rather than welded. This cable stop has two countersunk screw holes with 3mm diameter to allow for a M3 screw to be used to affix to the bicycle frame. The bottom of this cable stop is curved for tubing 20mm in diameter, so it's suitable for rear chain or seat stays. See my other larger diameter design for use on the bigger tubes of the bicycle. Please note, these have not been tested to any safety standards. Buyers use these at their own risk.