4mm DAT tapes

[IBMJunkman]

Any DAT data tape users here? Cleaning out for my move to Vegas. Found a stash of these tapes. Also found my Dad’s bulk eraser. I found it could erase 2 floppies at a time. I have no way to test how well it can erase the DATs. I don’t remember if they were pre-formatted. If I bulk erase a tape is it still recordable again for data? I see they sell on eBay but I don’t want to list them if my bulk erasing will render them useless.