The BBC Master contains a CMOS battery - this is often forgotten and leads to leaks which can seriously damage the internal components of the system.  This kit contains everything you will need to give your BBC Master a new battery:  full colour instruction guide, battery holder with reverse-charge prevention & self-adhesive back, 3 x Brand-new alkaline batteries and a cable tie.

The original capacitors in the BBC Micro power supply often fail on switch on with a loud bang and a puff of smoke.  It's good practice to replace them if you're refurbishing a BBC or just purchased one with an unknown history.