Mul-T-Lock NE10 Open-Shackle Padlock with an MTL300 cylinder. This product comes with two keys and a plastic card which is the only way to get additional/replacement keys cut for your lock.
 
The Mul-T-Lock series of padlocks have a high reliability in all conditions, providing excellent resistance against physical attacks and maximum resistance against weather and other environmental conditions and impacts, such as corrosion. Any padlock can be keyed alike, keyed different or master keyed for optimal access control.