... copper exposed or visible.2. No stratification, burr, sripe,pit etc in the side of rivet head3. no liable to oxidization ... small and medium-sized current contactor,starter,temperature controller,switches,etc.undercurrent contact devices,microswitches and precision instrument.Dimension: ITEMHEADDIAMETERD mmHEADTHICKNESST ... <10±2≥10±0.2R±2 electric silver contact for switch,temperature controller etc