This box has 2 templates in it. One for a 6 inch strike plate and the other for a 1"X4" T strike plate. They are made to allow a router to quickly cut out the recesses for door hardware.
Either template can be used if the dimensions fit the hardware you are using.
Check Templaco.com for more info on how to mount and use your router for the job. Eliminates the long task of hand drilling and chiseling the recess.