Here are new unused 8" x 5/8" (.625) ferrite rods.  These rods are slotted and perform exactly as good as the solid type that I have sold hundreds of over the years.  I have used them to build filament chokes and HF baluns and I do not notice any difference. I use short pieces to make my beverage transformers as well. They are the same H1000 material as the solid rod, also referred to as soft ferrite. These rods are also used industrially in the hf seamless tube welding machines. I can offer them at reduced price as a few boxes were sent by mistake a few years ago.  Their mistake is your gain !