A：
Large hole models， spherical， pinching，
Three different sizes rubber band，
Minimum circle diameter 2.5cm， diameter 2.8cm or more can be used
The tube is graduated and there is no simulation
B：
Small hole section， pull ring-like， stretch， and more effort
Three different size rubber bands
Minimum circle diameter 1.9cm， diameter 2.3cm can be used，
A silicone simulation inverted mold， no requirement on the diameter， then fine can also be used