Laser Pen 
This inexpensive and lightweight laser pen is useful for ray optics demonstrations and simple diffraction work. In addition to this you can make your point on overhead images with this useful presentation tool. Very tight beam for a small spot , Class 2. Less than 1mW so approved for use in schools. Wave Length 630-640nm. Powered by 2 x Heavy Duty AAA cells (supplied). Momentary push button operation. Suitable for KS3+.