What does "(L)" mean after a boss name looking for upgrades?

The title says it all. Under Upgrade Finder, I see 1) Si’Vash no L, then 2) Kil’jaeden (L). What does the (L) mean?

I am exclusively searching for LFR upgrades.


L is short for LFR. Some bosses like world bosses don’t have different difficulty versions, so there is no difficulty indicator after the name.