The incandescent 40W, 60W, 75W and 100W watt light bulbs are so iconic it seems odd to learn that the industry standard way of referring to these bulbs, "A-shape," means "arbitrary spherical shape tapered to a narrow neck." Whatever you call it, some of these traditional bulbs are being phased out in favor of more energy efficient Halogen, CFL, and LED equivalent replacements. The phase out applies only to the above wattages in the A19 shape with medium screw base. We will sell the phased out bulbs until inventory is gone. There are many other A-shaped bulbs unaffected by the phase-out.
The number after the A indicates the diameter in 1/8 inch (0.125) increments. For example, A19 has a diameter of 2.375 inches.