There are four different types of tablets - all available in packs of ten. All are oak, and the holes are made by burning which results in a smoother hole than drilling.
There are square tablets with 5 holes - the standard one in each corner plus a centre hole. These tablets also come with a 'Beginning Tablet Weaving' sheet to help get you started.
I have also produced a square tablet with 9 holes. Nine I hear you ask - well, the tablets found in the Oseberg Ship burial have quite a variety of hole placements (though it appears that the tablets were still only traditionally threaded). My 9 holed tablets combine the different hole placements in one tablet (and have an additional centre hole), so the advanced weaver could really get adventurous with these!
I also have 3-holed triangular tablets, for those of you who wish to try Roman weaves, and 7-holed hexagon tablets - 6 side holes and a centre hole.