This bottle is leak proof. My 8 eight year old can handle it. It's 18/8 stainless steel written on the bottom, meaning it shouldn't rust and should be tasteless because of it. The size is a little smaller than plastic with the same capacity - I tested. The bottle itself is a few grams heavier than plastic, meaning that you couldn't tell the difference in your hand. The cap might be the lightest of any bottles so I can feel that the complete bottle with cap is lighter than my other leak proof plastic bottles with the same capacity. Without the need for insulation, the cap is hollow - hard plastic with an integrated seal at the screw ends.I had a hard time finding a leak proof bottle, safe health wise, since my youngest kid was in kindergarten. There is about just one with leak proof caps that she can operate and easily drink from. I would trust it enough to put in in the backpack with books and papers. It is plastic because there's no other choice. I must have written reviews for the brand because I brought a lot of them, different models over the years.Eventually all my kids use stainless steel bottles, double wall insulated, with the same absolutely leak proof cap and easy to drink from. It's relatively expensive but I thought it was one off. It was not light and not slim, like carrying a big coffee mug with them. The problem is kids drop bottles. The steel frame hardly made a dent. But the hard plastic cap can't survive drops after drops. Or else the internal mechanism broke leading to leaks. I kept replacing the caps but it was almost as expansive as the whole bottle.In the end I gave up on stainless steel and moved back to plastic. Well, until I saw the new researches on plastic and how that the results are not supposed to be used other than as scientific research. The maker of my plastic bottles have the grace to give us the plastic material they use, Tritan. I wanted to switch back to their new style of steel bottles but they cost well over 2 to 3 times this.There's no point to use the bottle for anything else other than water (or flavoured water) at ambient temperature. Metal is the best conductor and cold and hot drinks will lost it's coldness and hotness very soon. If you need that you need double walled vacuum sealed steel bottles for example. They cost more and weight more.The cap screw has few turns and steep. I recognize that it's the same as my older leak proof steel bottles. It works and not too tough for my 8 year old. So she will have one too.18/8 stainless steel should resist rust, are used in pots and pans, and should not give you metal taste. I have reverse osmosis water at less than 30 ppm TDS and I don't taste anything other than tasteless water from the bottle. Since steel surface is not as smooth as plastic, for example if you use it for flavoured drinks, let it dry and not cleaning properly, you may taste the residue of it when you drink water.The bottle may dent when dropped, but I doubt if it's possible to make a crack. The hollow sturdy plastic cap should be better at absorbing shocks than the bottle itself.My bottle came as the picture. If you need a clip the hardware store has plenty.Update: 11/2014The bottle body hardly dents but all happens at the bottom. Therefore occasionally the bottle cannot stand straight up. A little knock on the concrete patio or mullet or hammer will fix it. The paint chips off at the dents. I would prefer the unpainted brush steel version but I need different colors for the kids. Also, some other old steel bottles and cups of mind have paints that chip off more gracefully.