The C Series caps are straight-sided, thin-walled closures designed to protect threaded connectors. The flanged end allows for easy installation and removal in difficult to REACH areas. This versatile design is ideal for a variety of threaded and non-threaded applications. Easy to install and remove. These caps meet nas-813 specifications.:: cap thread: 3, a: 2.980, C:.62, D: 3.22.