Start with the screen size
14 inches is now the most common size for work laptops, and several bags here keep the laptop apart from your papers so it does not press on them. For a 15.6 inch machine, look for a sleeve around 38 cm wide: laptops of that size measure between 35 and 36.5 cm. One full grain leather messenger takes up to 16 inches, MacBook Pro included, in a padded compartment. Bags sorted by size: 14 inch laptop bags and 17 inch laptop bags.
Full grain or top grain
Full grain keeps the natural surface of the hide and its grain; top grain cowhide is cut from the upper layer of the hide. Both develop a patina, and light scratches blend into the grain over time. Each product page states the leather and the lining.
Frequently asked questions
How do I know my laptop will fit?
Measure the width and depth of the machine, not just its diagonal, and compare them with the sleeve size given on the product page.
Can leather handle rain?
A short shower, yes, if you wipe the bag afterwards and let it dry away from heat. A conditioning cream once or twice a year limits water marks.