Metal urinary catheters. Generally made of titanium steel or pure titanium. The following are common sizes:

13.5 mm thick
10 mm thick
13 mm thick
10.5 mm thick
11 mm thick
9.5 mm thick
12 mm thick
12.5 mm thick
14 mm thick
9 mm thick
11.5 mm thick
8 mm thick
8.5 mm thick

Custom sizes are also available in addition to those listed above.