These are great, good quality straps, and the rubber coating means you wont dent or scrap your car. although lockable, and will prevent opportunist type removal of your kayak, or indeed theft of the straps themselves. Obviously they wont prevent concerted efforts with a blade to cut the straps, although they apparently have strengthening within the strap itself to reduce this as well..
I also use these to secure the kayaks in storage, on the covered racks at home. I'm not in a position to comment on whether they are suitable for long term exposure to the British weather, but they appear to be fairly robust and well made.
