What size Apple Watch bracelet is suitable for a 17cm wrist circumference?

In addition other Idris' excellent reply, there's also bands that offer specific sizing.

Like the Titanium Milanese Loop:

Natural Titanium Milanese Loop - Medium - Apple

17cm would be 170mms, so would fall under the "Medium" size (155mm to 185mm wrists) as shown in the link above.

Some of Apple's bands are adjustable or stretchy and are listed as "fits most." They don't come in different sizes. For example:

46mm Anchor Blue Sport Loop - Apple

Others come in sizes and give instructions on how to decide. For example:

46mm Turmeric Braided Solo Loop - Size 0 - Apple