Quality Park® coin envelopes are the perfect size for the small items you need to contain. Our coin and small parts envelopes hold keys, stamps, coins, seeds, medication, jewelry, charms or any small parts you need to store safely. Made of heavyweight 28 lb brown Kraft stock that's thick and durable enough to hold up to regular home or office wear. These Kraft envelopes are gummed with a moisture-activated adhesive for a strong, durable seal. 28 lb Bond Weight Kraft Stock. Seam Type: Center; Flap Type: Square; Trade Size: #5 1/2; Security Tinted: No.