This is a holder for your Raynox 250 cut into a K&F magnetic lens cap. Please note the Raynox is also turned down to save more weight. The diameter of the holder for the neck of the Raynox is around 44.25 mm which matches this holder. Make in one piece with supports. After it is printed and supports are removed you will need to slide a razor blade under the "tabs" to break them free allowing them to bend. I made mine out of PLA. Enjoy :)