All Supakit collars come with a friction-based breakaway buckle (this is the black buckle in the middle of the collar that has the Supakit logo on). It's designed to open when pulled apart.
Opening the collar when it is not on your cat
To open the collar, simply take the left and right side of the buckle in each hand as shown in the picture below, and pull apart firmly. The left and right side of the buckle will come apart.
Opening the collar when it is on your cat
To remove your cat's collar when it is on your cat, simply hook your index finger of both hands behind the buckle, pinch the buckle between your index finger and thumb, and then pull apart. With a little bit of practice, you should be able to use your hands to absorb any sudden movements as the buckle comes apart, leaving your cat none the wiser as to what has been going on!