A K31 repair kit is a set of tools and parts used for the maintenance and repair of the Swiss K31 rifle. This could include items such as replacement springs, screws, pins, cleaning tools, and other components that might wear out or become damaged over time. The specific contents of the kit can vary, but its purpose is to help ensure that the rifle continues to function properly. It's an essential kit for gun owners who want to maintain their firearm's performance and longevity.