Protect your stuff and make sure it stays on the rack with Thule Lock Cylinders. They're made in one size that works with all sorts of different Thule rack parts so you can get a package of Lock Cylinders and lock everything up with just a single key to keep track of.
When I got my new truck it came along with a nice rooftop rail system right from the get-go, but the only problem was that it was locked in place, and not in the right spot for my bike racks. I snagged these lock cylinders to replace the locks and get things going. The one frustrating bit is that the universal key for changing the locks doesn't actually work on a locked-lock (which makes sense when it comes to keeping your racks secure from other folks with universal keys), but this posed as a challenge for removing my original cylinders. After a trip to a locksmith I was able to get them swapped though, and now it's smooth sailing with these new cylinders.
It's a lock for your Thule stuff, pretty simple. Only complaint is that you can't buy new locks that match up with your existing ones so you don't have to keep buying new sets. Not sure if this is a feature that Thule will allow if you buy through them, might be worth investigating if you need something like that.
After spending good money on a nice bike & rack, picking up some locks is a no-brainer. They won't guarantee you bike's safety, but do provide peace of mind should you need to step away. I've been using Thule's lock cylinders for a couple years now and haven't had any issues.
If you want to keep you gear safe and locked up then these are the lock cylinders you need. Have them on my Thule mount system for my Jeep and I can sleep well at night knowing that they will be there in the morning.
I purchased the lock set to pair with my AeroBlade rack system. A small part of the package, but wonderful for giving you peace of mind that someone will not run off with your gear. Well worth the money.
If you plan on keeping you thule locked to your car these are a must need. Anyone that has a little bit of thule knowledge can yank the rack right off your car in a matter of minutes if they are not locked. Easy buy here no brianer