What is Reddit's opinion of Gadget Zone UK Heavy Duty High Security D Shackle Bike Lock | Suitable for Regular & Large Bike Frames - Bracket Included?

From 3.5 billion Reddit comments

Pro: almost like a chain, makes it just a bit more difficult to work with than U locks but can be made from hard but relatively lightweight metals. Can be stored easily, low profile and there are usually frame attachments. Should be ok for quick stop at the shops.
Con: Not a chain, has multiple weak links instead of each link being the same strength, at worst can be propped against the bike frame and forced open (absolutely no cheapos). Easy to cut with a grinder and does not need vicegrips and second set of hands.

Chains are imho the best, they are flexible but strong, and what makes them flexible also makes them harder for the thief. Soft durable cover made from kevlar or similar fiber will make it even harder to get a good hold. They tend to get fairly heavy, so buy a proper bag, pouch or box where you store it while traveling.

And as we are at it, cable locks are rubbish. U locks are ok, they can be made from extremely hard metals. Chains are usually more ductile because of the way they are made. Grinder attack is undefeatable, bolt cutters can defeat cables and cheap locks of any type. Picking is rare but at least.. get a lock that can't be raked in 2 seconds (most tumbler locks) and avoid tubular locks as well (basically, don't buy this lock, i know, i got one, it is not securing anything valuable.. avoid that key type). Disc retainer locks are the best, there is no fast way to pick them unless they are dirt cheap clone of a clone of ABLOY.