You get 2 of the Top Star MODEL SL-728, SL728, new old stock, heavy wear on the packaging.

This is a TOP STAR Electronic BAllast, 105W max output and a minimum load of 20W.  These are used to step 120V down to 12V for halogen light bulbs.  This is a replacement for those fixtures that need to strattle the stem in the canopy.  

IMPORTANT NOTE: Low voltage electronic transformers must be tested under load with a analog meter to achieve accurate results. Testing the transformer with a digital meter will produce an invalid reading of "no output". This characteristic is unique to electronic transformers that produce a square sign wave. We recommend use of an analog meter for testing with the transformer loaded to at least 20% of its rated output. Most electronic transformers returned as defective are actually good due to testing methods in the field that did not follow the above requirements.