What are the key factors to consider when choosing a mountain bike stem?

When choosing a mountain bike stem, key factors to consider include the stem length, rise, material, and compatibility with your handlebars and fork. The stem length affects the bike's handling and comfort, while the rise determines the height of the handlebars. The material of the stem can impact its weight and durability. Make sure the stem is compatible with your handlebars and fork to ensure a proper fit and performance.