These are the bolts that hold the jingles onto IVSOM chocalhos. After years and years of playing a chocalho the friction between the jingles and the bolts will cause the bolts to wear thin and break, as you can see in the photo here.
We also carry replacement aluminum or steel jingles. As the bolts are wearing thin from the friction, the jingles are also wearing out. The hole is getting bigger. When the both fail usually jingles fly all over the place! It's a good plan to replace them before all of that happens.