It definitely is one of the S. makinoi. Could be either 'Limelight' or 'Ogon'.
Growing conditions can make it tricky to tell the two apart. Both are only hardy to zone 6. With some protection it might make it in your zone 5b.
Beautiful photo of a beautiful specimen of a makinoi type of sedum.
Does either of those names sound familiar as to what was on the missing tag?