A strange little fare. Good also for DFW r/t. This is not BE. Books into K class.
3600 miles with 500 minimum flying SFO-DFW-IAH-SFO. Good every day of the week January 10-March 7, 2018.
It's difficult to find on united.com because it will not appear as the cheapest fare outbound to take the 10:40 a.m. flight SFO-DFW, but the return flight books at $44 bringing down the all in price to $179.
Here's a google flights link:
https://goo.gl/flights/LZ4t