I sent the following off to Brownell's:

"Department: Technical Support (GunTech)
Order ID:
SKU: 080-943-213WB (.213\") or 080-943-022WB (.215\")
Message:
I need one of the pilots above, but do not know which one to
order. It will be used on a Remington 552 and a Remington
550. Can you help me out?"

.....and got the following answer:

"I would start with the .213", if it is too loose than go up to the .215"."

Since this is going to be used only twice, I sure as heck do not
need a spare that will never be used lying around!

Does anyone here know Remington's land-land specs for their .22RF's?