No not size, sim card model. Every phone registered on the Sprint network typically has a sim (ICCID chip) for LTE coverage. They have cards that work with multiple phones, but cards are not interchangable. Ex: pixel 1 card can't be used in a pixel 2, but can go to another pixel 1 or any other phone that takes the same model card. But they can be reused and do not store personal info. I think it goes by phone generations typically. Do a quick search for cards and you'll see what I mean they all have different product codes. I've never activated an unknown phone before on the network so let's see how this goes. I think Verizon customers will have to varying degrees a semi similar problem
Your SIM, or Subscriber Identity Module, does have a number associated with it, called a SIM serial number (SSN). This number is also referred to as the integrated circuit card identifier (ICCID). ICCIDs are stored in the SIM cards and are also engraved or printed on the side of the card.
The format of the ICCID is: MMCC IINN NNNN NNNN NN C x MM = Constant (ISO 7812 Major Industry Identifier) CC = Country Code II= Issuer Identifier N{12} = Account ID ("SIM number") C = Checksum calculated from the other 19 digits using the Luhn algorithm. x= An extra 20th digit is returned by the 'AT!ICCID?' command, but it