These Alcyon handcuffs, National Institute of Justice certificated, are double locking with a pin situated on the keys.  They are finished in black oxide and would be suitable for undercover or swat teams. 

Type of Link	Chain
Key	Standard
Construction	Riveted
Mechanism	Double lock treated
Toothed	Double
Weight	350 grs.
Length	235 mm.
Minimum opening	50 mm.
Maximum inside perimeter	165 mm.
Minimum inside perimeter	200 mm.
Locking Position	20
Construction	Steel K-60
Rockwell B Hardness	HRB-92
Thickness folded	18 mm.
Complies with salt spray test and resistances tests