I have my suspiscions about caps that can be poured through. I fear that they would leak if I stuffed them in my pack and then fell backwards by accident (as occasionally happens to me) I use screw-top aluminum fuel stabilizer bottles with gasketed screw tops. I will look up the brand next time I'm in my trunk. Nice and strong and light and 4 oz in size. 1 works fine for a 3 day hike solo and they are small enough that I don't have a problem sticking a couple in the pack.