Which of the following is primarily used for smoking cannabis in small amounts?

Using one hitters is specifically designed for smoking cannabis in small quantities. These devices are characterized by their compact size and are optimized to deliver a single inhalation of smoke, making them ideal for discreet use. One hitters allow users to control their intake precisely, as the small bowl can hold just enough cannabis for a single puff, reducing waste and ensuring that only a small amount is consumed at a time.

While pipes can also be used for smoking cannabis, they typically accommodate larger amounts and are not specifically designed for single-use scenarios. Vaporizing devices are intended for a different method of consumption altogether, utilizing heat to transform cannabis into vapor rather than smoke, which doesn't align with the intention of the question. Stash cans are often used for storage rather than consumption. Therefore, one hitters distinctly satisfy the requirement of smoking small amounts of cannabis.