Eufy Baby Smart Sock Track Sleep Patterns, Naps, Heart Rate, Blood Oxygen Levels. AI Cry Detection No Monthly Fee. What's In the Box：Sensor; Socks × 3; Base; Power Adapter; Power Cable; Quick Start Guide. Features & details Monitor What Matters Most from Anywhere: Have peace of mind knowing your baby's vitals are always being monitored and always available on your smartphone. A Full Picture of Your Baby's Wellness: Track more than just regular sleep patterns, including naps, heart rate, and blood oxygen levels. Get daily sleep reports based on customizable sleep tracking sensitivity. Know When You're Needed: Get instant notifications when your baby's vitals change or the sock detaches. Customize the alerts you want to see for a personalized parenting experience. Optimized for Accurate Data and Reporting: Get customized tracking and reports on your baby's sleep patterns with optimized algorithms and a fresnel lens. See key data like heart rate and blood oxygen levels over the past 48 hours. Comfortable and Easy to Wear for 0–18 Months: Smart Sock is dirt-resistant, flexible, soft, and washable, coming in 3 sizes so it grows with your baby. HSA/FSA Eligible. This comes with small, medium and large sock, small sock is slightly used but in very good conditions.