All the tires we sell on this site are air-filled. Within an air-filled tire is a tube. That tube is subject to puncture just like a bike tube. You can either patch it, or you can replace it. One word of advice – when you put the tube into the tire, throw a little Baby Powder in to reduce friction. I think buying a spare tube for your trailer is overkill, unless you’ll be in a remote place for a long time, as they are usually available at any bike shop. The odds of you needing a new tube are pretty slim, but if you want to be prepared, an extra never hurts. Just like a standard tire or bike pump, these tubes use Schrader valves.