This Advanced Encryption Standard (AES) algorithm parameter ASN.1 type CFBParameters is defined as

    CFBParameters ::= SEQUENCE {
       aes-IV        AES-IV,
       numberOfBits  NumberOfBits
    }

    AES-IV ::= OCTET STRING (SIZE(16))

    NumberOfBits ::= INTEGER(1..128)

Also see AES_IV and NumberOfBits.