There's no such thing as Contact SL from regular Union line, it's something specially made for Sierra. SL highbacks come from Force SL and rest are basically Contact. Have tried both Contact and Contact SL, and I think highbacks from the regular Contacts are a better match. By the way Sierra Contacts are sold out long ago so best bet would be Ebay, maybe. Fucking lite or Flite looks almost identical if your attracted by the color ways of Con SL, although base plates and high backs aren't the same.