Kryptonite Keeper 5 Mini Disc Lock. From the brand that invented the U-lock. This brake disc lock is small enough to fit in your pocket. Snapped onto the disc of your scooter or small cc motorcycle, it will help prevent roll-away theft. 

• Compact, lightweight and weatherproof
• Dual-reinforced, high security, disc-style cylinder
• 5.5mm pin diameter fits smaller vent holes
• 2 high security, "I" keys
• Carrying pouch with belt-clip included
• Dust cover over key-wa

Important dimensions:
5,5mm - 11/32" locking pin
39 mm - 1 17/32" throat (pin to end)
7mm - 9/32" vertical clearance