You have new mail on a Remington factory 20" barrel cut to 18.1" by ADCO and threaded for a Tritium bead (new, included).
My 870 SBS paperwork came back so i switched to a 12" barrel, no longer need the 18". Mint bore.
email uxb at mindspring.com for pics. Price sent in email. Will try to post pics tomorrow as well.