The realy compact tracer unit fro Xcortech, the XTR301 is just around 2.5 inches long with over 1 inch diametre. It has built in 2 high power LED illuminators and also a built-in motion sensor that can sustain on lighting 35 tracer BBs per second. This has a rechargeable lithium battery that can charged using the USB charging port. The Tree Reviews takes a look at this tracer unit in this video review.