This is a shapemod to a mini 3x3x3 cube to produce a shape-shifting puzzle. The name comes from the fact that the patterns on the faces look a little like the math symbols for add, subtract, multiply and divide. As well as these parts, you will need to buy a Witeden mini (30x30x30mm) 3x3x3 cube which has to be slightly truncated (cut) along one edge to fit the extensions. The stickers were made by Oliver's Stickers and can be bought here
or you could make them yourself from adhesive backed coloured vinyl.