There are various bolts applied to attach different parts of a bicycle. The bolts on the brake, including the cable pinch bolt and brake pad bolt, are 4-5 mm in size. Speaking of the bicycle seat, 4-6 mm hex bolts are apt to attach the saddle to the post. 4-6 mm binder bolts are suitable to secure the seat post at the correct height inside the seat tube. 4-5 mm bolts are attached to connect middle and large chainrings. A 5 mm clamp bolt attaches the front derailleur to the seat tube. The size of other bolts ranges between 3-5 mm in most applications. However, the range alters as per the bike’s model.