So I am guessing the first question is.. What is Travel Sentry? It's a good question, they are a company who devised a standard for luggage locks so they can be opened by a Master Key by Airport Security - most notably the TSA (Transport Security Administration) in America. This means that instead of having to take some bolt cutters to your lock to make sure you're not smuggling in radioactive material or gun powder they can use their magic master key to open the lock, do the security check and then lock your suitcase back up and send it on it's way. No need to try and remember what one-year-ago-you decided was an unforgettable code, lock comes with two good old fashioned keys. "Yours & Theirs" twin pack so you don't have to arm wrestle for the last padlock. Here's a tip for keeping your spare keys, because we all end up with a drawer full of them - take a permanent marker and make matching marks (cross, circle, numbers whatever takes your fancy) on both the spare key and the lock. No more guess work!Dimensions (W/H/D) - 2.5 x 4 x 1.25 cmMaterials - Brass lock body with ABS coating, 100% Steel Shackle