The Owlet V3 Set of 4 Socks in Forever Rainbow is thoughtfully designed for use with the Smart Sock 3 and Smart Sock Plus Sensors and Base Stations (available separately). Each set includes 4 fabric socks for left and right feet in 2 Sizes, a Newborn sock and Infant socks. The socks fit babies 5 to 30 lbs. (2. 26 kg to 13. 6 kg) FEATURES 4 total socks(2 right + 2 left) in sizes 1 & 2 so baby can wear from 0-18 months old. Sensor and Base Station not included. Only compatible with Smart Sock 3. DIMENSIONS Size 1: up to 12lbs Size 2: 12 - 30lbs