This tall 4"" posture collar is created of thick, durable leather. It has a solid welded tri-ring in the front and a heavy-duty buckle in the back. While it can be used with or without a padlock, with the padlock the collar stays in your sub for as long as you wish. The padlock is sold separately. Small fits neck sizes 12.5"" - 14.5""; Medium fits neck sizes 15"" - 17.5""; Large fits neck sizes 18"" - 20"". This collar is a medium.