Harness Size Guide Please measure chest and neck circumference before purchase (please ensure you leave 2 finger size spaces between the neck) S: Chest: 17-25"43-64cm Neck: 12-16.530-42cm".This dog harness has fully adjustable sliding straps at the chest and neck and is suitable for small dogs. Safe & Comfortable High visiblity light up dog harness is made from 100% non-toxic mesh and polyester to protect your dog's skin. Adjustable chest and neck straps ensure a comfortable fit and a snug fit for your pet. Breathable air mesh keeps your dog cool during outdoor activities. Waterproof: resistant to daily rain, not to be immersed or swum in. Tip: Please avoid the battery compartment when cleaning. No-Pull & No-Choke & Easy-Wear Light up vest is designed with a no-pull back strap, the pulling pressure is evenly distributed across the body for safer dog walks. This no-pull Pet chest strap is perfect for everyday outdoor walking, running, jogging, hiking, training and more. This hassle-free dog overhead harness is easy to put on and adjust, this comfortable and breathable chest strap has a quick release snap closure for easy on and off. 3 Light Modes & Super BrightThis led dog harness has three modes: fast, slow or steady light modes. One key switch mode, fast switching. With super bright light and a visibility of 550 yards, this led dog harness improves visibility and safety for pets walking at night to avoid accidents. USB Charging & High Endurance The Led pet harness is designed with USB rechargeable, charging time is about 40 minutes and can be used last for 2-3 hours in constant light mode. Fast flashing mode approx 4 hours. Slow flashing mode approx 6 hours.Your dog will enjoy the daily walk in this comfortable dog harness!