At Marlin Beach, we use Full Grain Leather as our primary veg-tan for our belts and radio straps.
If you're wondering what that means, you;'re not alone, it is a frequently asked question. First, here's a little about Veg-Tan. Hides go through a tanning process to make them into the leather we know and love. Veg-Tan simply means that vegetation is used as opposed to oils and other ingredients. Veg-Tan leather will result in a smooth leather that can be "tooled" (placing a design on the leather) well while providing a thick hide.
Full-Grain merely means that the "skin" side (called the "grain side") of the leather is used and the leather will be 100% from the grain right through to the desired thickness. Assume, if you will, a piece of leather that, after being tanned, is 1/2" thick. That thickness (called the weight) is too thick for a belt and therefore the leather will be split into two pieces, each being roughly 1/4" thick. The part with the grain side is the "full grain" piece and the remaining piece is re-surfaced and usually called "genuin leather". The genuin leather is not as strong or sturdy as the full-gain piece and can therefore stretch. While stronger and more desirable, the full-grain piece will have more blemishes such as bug bites or scarring that you might expect from a living animal.