MR16 halogen floods at 20W, 35W and 50W on a 12V GU5.3 bi-pin base, from 260 to 825 lumens at a 36° beam.
These are low-voltage lamps and require a transformer — putting one into a line-voltage fixture destroys it immediately. Voltage and base are therefore stated before output on every SKU, and the bi-pin base is called out explicitly to separate it from GU10.
Display cases, low-voltage track and landscape fixtures are the installed base. The line-voltage alternative is GU10 halogen, and the LED conversion is in LED spotlights.