I bought one for my acetylene. I look at it like this. We spend $100-200 on a single grinder, Thousands on a welder, thousands on a bed, bevelers, torch and a host of other tools. After all of that what are two caps at roughly $45 apiece gonna do? Break the bank? I'd rather have them on there than have a wreck, bottle somehow comes loose, valve gets broke off and kill some 5 year old kid in a car. I see them uncapped and I call cause my wife and kid's travel the same roads. One truck from a door company had BOTH tanks laying down and they had them mounted on the flatbed behind the cab. The bad part was that the valves stuck out past the side of the cab, right there wide open. I just thought, holy crap, you gotta be kiddin'. I guess this is one of those thing where some folks will think I'm an a-hole cause I call, think what you will and I'm probably an a-hole but like I said, my wife and kids are on these roads too and the darn things cost around $100 for two.
http://www.rmiorder.com/index.php/browse/category/id/CAP/page/4