Amidon Ferrite Rods R33-050-750 R61-050-750 and thinner 10 mm x 160 for popular RFI, BCI disturbion feature. Three ( 3 ) Rod set, one of each = 1 pcs in the order. R33 models only 3 pcs. R61 models 5 pcs in the stock. After 1st three, the set will be 2xR61 and 1 x 10mm rod.