Aluminum is measured by thickness not gauge, so .019 is nineteen thousands of an inch thick and .024 is twenty four thousands of and inch thick. That may not sound like a very big difference but when it comes to how it performs its huge. .024 fascia lies flatter and you can cover larger fascia without it rippling. The cost is significantly higher but the results can't be beat. We use .024 aluminum trim coil to make all of our fascia, frieze and gable fascia coverings.