Please answer a question about the following article about Gymnastics:

The technical rules for the Japanese version of men's rhythmic gymnastics came around the 1970s. For individuals, only four types of apparatus are used: the double rings, the stick, the rope, and the clubs. Groups do not use any apparatus. The Japanese version includes tumbling performed on a spring floor. Points are awarded based a 10-point scale that measures the level of difficulty of the tumbling and apparatus handling. On November 27–29, 2003, Japan hosted first edition of the Men's Rhythmic Gymnastics World Championship.

How many apparatuses are used?
only four types