Full grain keeps the outer surface of the hide intact, including its marks. It is the strongest and ages best, and it is the hardest to buy consistently because every hide is different. Corrected grain has the surface sanded and a finish applied, which evens out appearance at the cost of some strength and breathability.

Split leather comes from the lower layers after the grain is removed. It is genuinely leather and genuinely weaker, and it is appropriate in linings and in some casual uppers where it is not carrying structure. Bonded leather is reconstituted fibre and belongs in a different conversation entirely.

The buying error that recurs is comparing a corrected grain price against a full grain price as though the difference were margin. It is not: they are different inputs with different yields, and a full grain programme needs tolerance for natural variation written into the quality standard before production starts.