According to Wikipedia, the ;cornet is a brass instrument that visually resembles the trumpet. It is not to be confused with the Medieval instrument, the cornett or cornetto. It differs from the trumpet in that it has a conical bore, a compact shape, and a mellower tone quality.
Glad we got that sorted out.
Dimensions: 29mm x 16mm (approx.) Weight per cufflink: approx. 5g (medium)
Size = x mm (W x H)