My trailer uses the 921 wedge type bulb. lots of info on here on what others have used to replace their 921 bulbs. I went cheap with the EBAY/CHINA $4.99 boards to replace mine. I had to go with non-regulator type LED boards as the regulated type LED boards produced low level RFI signals that interfered with my HDTV, NOAH WX RADIO, and Ham radio operations especially when I was using the OTA Crank up BAT WING and camping off the power grids.
If you buy the high dollar type only buy ONE and try it out before spending lots of money only to find out you don't like them...
Roy Ken