Silicone is a type of synthetic compound made of silicon, oxygen, and other elements. There are many different kinds of silicone. One kind is a liquid and is commonly used as a lubricant to reduce friction between moving parts. Unlike petroleum-based lubricants, silicone is nontoxic. However, silicone is more expensive than petroleum-based lubricants.

Which of the following would silicone lubricants most likely be used for?