I was going to buy two Kryptonite Evolution Series 4 disc locks, but after looking around, it was suggested that the Kryptonite New York were better. A bit of youtubing has put me off them as they seem a bit insecure. I next looked at xena alarmed disks and oxford monster, but again, they receive many mixed reviews(!) The xena supposedly not waterproof, rain causing them to malfunction. I'm open to suggestions on the most secure disk locks to get - I don't mind paying a bit for something which is going to make a difference.