Note: the information below refers to the long ballpen refill as used in the Diplomat, Viceroy (standard, not Pocket), Deluxe 60, Corinthian, Deco, Perfecta, Sceptre, Regent, Edwardian and similar models.
Many years ago, Yard-O-Led used a refill like the one at the top of the photo above. In more recent times (perhaps 20 or more years ago) the refill was changed to the one at the bottom of the photo. Pens that were originally made to take the top refill cannot use the bottom refill as there isn't enough space in the barrel.
In 2015, Yard-O-Led changed the refill to revert to the older type (the top refill in the photo). This is good news for Yard-O-Led ballpen owners as this "new" older type refill will now fit all Yard-O-Led ballpens regardless of age (except Pocket models and Retro/Astoria).
So, if your refill looks like the one in the top of the photo, we have these in stock. If your refill looks like the one in the bottom of the photo, don't worry as the one in the top of the photo is compatible.
Note: Yard-O-Led Retro and Astoria models us a Parker style (G2) refill. This type of refill is not compatible with pens that use either of the refills in the photo above.