2XU Invisible Socks 3 Pack Accessory size:Medium QZSS GNSS Chipset All Satellite Dual Frequency Shoe size:UK 9.5 QZSS GNSS Chipset All Satellite Dual Frequency Navigation Map Layer Landscape Pre loaded Global Maps Topo Downloadable Regional Maps Additional Features Checkpoint Back To Start Deviation Alert Touchscreen Enabled Map Control Data Tracking Sensors Optical Heart Rate Monitor May not work over tattoos Barometric Altimeter Accelerometer Gyroscope 3D Compass Thermometer Supports body temperature in training (with compatible accessory) Optical Pulse Oximeter Electrocardiogram Sensor Training Features Resting Heart Rate Underwater Heart Rate Action Camera Control Supports select GoPro and Insta360 cameras Virtual Pacer Virtual Run Running Form Test Requires COROS POD POD 2 Altitude Mode Regular evaluation of SpO2 and fitness when at high altitudes Touch Scroll Swipe to scroll data pages during training Extender Daily Features Stopwatch Daily Alerts Include active calories Lightweight bonded drawstring waistband for an ultra comfortable secure fit Quick drying moisture wicking fabric 17% POLYESTER