Inverted design prevents light rays from affecting the sensor 18" sensor spacing for improved accuracy each unit factory calibrated to within +/- 0.25% accuracy Built in LED Light Kit Ideal for firearms, archery, airgun and paintball Simple operation, large LCD screen Meters per second or feet per second reading Bluetooth to interface with smartphone Rechargeable Lithium Ion battery App displays velocity, logs, data, notes, weather conditions, easily exports via SMS or Email Carry bag included Heavy duty tripod-Height adjustable from 15" to 42" and includes 1/4-20 dovetail plate to attach to the chronograph for Mfg: Caldwell Shooting Supplies