Size XS: Suitable for neck circumference 28-38cm, width 2.0cm, total length 41cm Size S: Suitable for neck circumference 34-41cm, width 2.5cm, total length 44cm Size M: Suitable for neck circumference 37-46cm, Width 2.5cm, total length 50cm L size: suitable for neck circumference 41-52cm, width 2.5cm, total length 56cm XL size: suitable for neck circumference 42-56cm, width 2.5cm, total length 60cm [Function introduction]: Each model has a hidden switch, with 4 functions: fast flashing, slow flashing, static flashing, off. With a button battery (remember to take off the collar when taking a shower, just pull out the battery box), button batteries can be bought in supermarkets! Color options: red light, yellow light, green light, blue light, orange light, pink light, white light, colorful (white light is the same color as the colorful webbing) 4 lighting modes: long light, fast flash, slow flash. Off (controlled by switch)