Ideal Brand 18 inches x 500 feet Aluminum Foil Roll. Standard Gauge.  Choose this side when you need to wrap larger food or line larger pans. This roll is an ideal size for use in a restaurant kitchen or for personal use at home.
Aluminum foil will do a better job of retaining moisture in food compared to Versus plastic wrap.
Note, it makes no difference which side of the foil you use.  The difference in appearance - dull and shiny - is the result of the manufacturing process.