Garage doors have steel panels that vary in thickness. Low-cost doors have thin panels of 27- or 28-gauge steel. Though inexpensive and suitable for many garages, these doors will not stand up well to impact (from basketballs, for example).
Midlevel doors offer 25- or 26-gauge steel (the lower the gauge number, the thicker the steel). Top quality doors use steel that is at least 24 gauge. Commercial-grade doors use even thicker steel. Some steel garage doors offer thicker steel on the outside than on the inside.