This is a set of 3 pieces of 2.5mm diameter Spring Bars. They have thicker 1.1mm tips than the usual spring bars and they are designed for diver's watches, such like Seiko watches, and are normally referred to as "Seiko fat spring bars".

We also stock Style spring bars, which have a slightly thinner (2mm) body but still with the wider 1.1mm tip end pieces.