Bigger is always better. In all seriousness the larger labels have more surface area and thus a bigger circuit printed in them. The larger circuit makes them resonate stronger and the antenna can pick them up easier. If your items have room for a 1.5' x 1.5' label we recommend you use a 1.5"x1.5" label. If not the 1.18"x1.18" label is still a good choice. Labels smaller than this become problematic and don't protect your inventory to the same degree. The exception to the small label rule is the Sensormatic style label for AM 58KHz system which functions very well even with its diminutive size.