What are the main arguments that a set consists of 7 pieces?

In fact, a set of distorting mirrors consists of 3 shapes and the counter shapes. So a concave length versus a convex length etc. And when faith was regularly asked for a straight mirror (because God sees you as you are) we decided to also add a straight mirror in the same design to the series. We now also have a Nr8. A Bol / Tilt forward mirror to replace the straight mirror as people who do not want to purchase a complete set. And we also have a No. 9. Bulb to the right, here we place a screen behind the straight part. Naturally we then use espionage mirrors.