The 2.4 inch 61 core is part number 5961003821. I use them for stack match transformers from time time or for small baluns wound with RG142. 13 turns of RG142 on a single core give me 30uH, same as my solenoid chokes. 73 Peter You use these for Hy-Gain TH7 antennas? 73 Jim W7RY