Standard prong length (3.5mm) caps are very short and should only be used for very thin material like a single layer of grosgrain ribbon or doll clothing. Please note however that your material may be more prone to ripping over time if you are only using a single layer. Standard #14 snaps install best with a table-top press. Pliers are not always able to apply enough pressure to flatten such a short prong sufficiently.
Please note: I am not a Kam Snap dealer.