The Model Train Technology™ Speed Stick™ is a portable and highly accurate speed measuring device for model trains from Z to G gauge. It is small enough to sit on the side of the track and comes with a built-in 500mAh rechargeable lithium battery. The Speed Stick can be run on the battery or can be plugged into a USB-C cable to run on any 5V phone charger! There are no batteries to replace! The Speed Stick uses Precision Detector technology which is extremely fast and is precise to 1mm. We do not use reflective IR sensing. As a result, the Speed Stick is immune to changes in ambient light conditions. It will work outdoor and in a completely darkened room. Auto-Ranging mode is built in. This allow you to set the sensor range to the edge of the first rail of your track so that it will ignore objects (or trains) that are just beyond the track of the train you want to measure. The maximum range is 150mm (5.5”) from the from sensor side of the Speed Stick. INCLUDES: Speed Stick, USB to USB-C Charger cable Selectable Scales in the unit: Z scale = 1:220N scale = 1:160HO scale = 1:87S scale = 1:64O scale = 1:48G scale = 1:22.5 (note fastest measurable speed is 74km/h) NK scale = 1:148 N scale UKTT scale = 1:120 Table topOO scale = 1:76 Most Common in UK close to HOOE scale = 1:45 Europe O scaleOK scale = 1:43.5 UK O scale