The new Smart Sock 3 Extension Pack works with your existing Smart Sock 3 sensor and includes our toddler-sized fabric sock.Track your child’s heart rate, oxygen level, and sleep trends for 42 additional months for continued peace of mind.Track heart rate, oxygen level & sleep trends.Access to 42 additional months of live readings.Tailored monitoring technology as your child grows.Large fabric sock works with Smart Sock 3 sensor. For children approximately 13.5 to 25 kg.Price: $109.00Category: Nursery-OwletManufacturer: Owlet