For the sale of Handcuffs into NSW we require a copy of your security licence.  Whilst other states do not require a licence to posess, the use is highly regulated

Heavy duty double locking steel hinged hand cuffs with welded chain links made from quality carbon steel. The double locking feature allows you to lock the cuffs down to prevent the detainee from closing the cuffs too tight on the wrist. 

• Made from quality carbon steel
• Double lock system assures security
• Smooth ratchets for swift cuffing
• Two "Guardwell" keys included

Hinged handcuffs? They can be a game changer. I think any cop that keeps up with current trends has seen the videos all over the internet showing how standard chain link handcuffs can actually be defeated at the swivel point if the suspect is cuffed with their hands in front. Hinged cuffs reduce the chances of a suspect being able to use the leverage of the swivel and chain to snap the cuffs to free their arms. They also make slipping the handcuffs from the back to the front by tucking their legs up more difficult because the hinged-style cuffs reduce the flex of the wrists. I will say that one drawback to hinged cuffs is that they can make handcuffing an actively resisting suspect a little more difficult because both wrists need to be lined up straight since the cuffs lack that old-style swivel to accommodate the odd handcuffing positions.