A guy with no arms but the arms are long. Now that's a concept.

"So you're saying you have no arms."

"That's correct."

"But that they're both six feet long."

"No."

"Oh. Phew. I was confused for a second there."

"I have no arms that are eight feet long."

"What? But surely you could easily say you have no arms that are fifty feet long as well or any length. I sure have no arms that are fifty feet long, even though I have two arms of perfectly normal length. You just have no arms."

"Well, that's just it. The arms I don't have are exactly eight feet long."

"Oh, so they're missing, is that what you're saying?"

"No. Never had arms. It's just that the ones I've never had are exactly eight feet in length."

etc.