PC8-02PC represents a straight thread, and 8 represents the outer diameter 8MM trachea,02 on behalf of the British system of 2 points (all threads are British tube threads)[snail description]: M5:M5*0.801: (G1/8, commonly known as 1 points) the outer diameter of the thread is about 9.7MM02: (G1/4, commonly known as 2 points) the outer diameter of the thread is about 12.7MM03: (G3/8, commonly known as 3 points) the outer diameter of the thread is about 16MM04: (G1/2, commonly known as 4 points) the outer diameter of the thread is about 20MM