Steel-Line Garage Door bought Boss Openers in mid 2016. All Boss garage door opener remotes made since 2016 have Steel-Line branding. This can cause some confusion, however, we have a handy guide for finding the correct remote control!
The original HT4 2211-L (TX) Boss remote is replaced by the 303-RTX. This is the new version of the same remote, made by Steel-Line. It, however, will not work on boss roller door motor. You would require the AOHT4 remote, which operates the same as the original boss garage opener.
If your remote control has three buttons and a red LED, you need the HT3 remote control.