Small World Toys Science - Room Alarm Lab Experiment Kit Discover how a burglar alarm works with the Room Alarm Lab from Small World Science This kit includes everything your child needs to build a working alarm for the bedroom door The alarm measures 3.5''W x 3.5''H and requirse a 9V battery (not included) 'Keep Out'' sign included with the kit - suitable for children 8 and over For 50 years, Small World Toys has delivered fun, safe, innovative and endearing products for children of all ages