They're a unique flat design that can be made to look like a postcard (based on an actual design that enabled radios to be sent through the post!)
The radio is assembled by soldering just 2 components on to a printed circuit board. The coil is 'printed' on the board and tuning is done by moving a metal plate over the coil. (batteries are not required!)
Each radio pack makes 10 working radios each complete with crystal earpiece and aerial wire. Self-adhesive postcard graphics are also supplied. Bulk Pack for 10 Students.