Don't order these from Cruiser Customizing. I just found them on the Ride-On website
for a couple bucks cheaper ($34.99). You can also get a 4-pack ( I assume for cars) for $69.99, but it only comes with one Roadside Assistance certificate, which isn't a big deal to me since my insurance covers roadside assistance.
The 4-pack has appeal since I'd want it for my wife's Stryker as well. She's worse at keeping up on her air pressure than I am.
The 4-pack also looks like it only contains one of the locking keys, so that could be an issue.