I have arthritis in my hands so attaching to cage is somewhat difficult as the spring does not stretch very easily but overall a good buy for the moneyI have pet rats, these glass bottles are the best. The rats prefer them and they don't leak.There is nothing wrong with these water bottles. First I ordered one just in case all the negative reviews were right. It worked fine, the reviews are due to user error, not the bottles. I have since ordered 3 more & that will not be my last. All 4 water bottles are in use & working with no issues. None. Zero. Nada.I like to mount the water bottles on the outside of my rabbit cages. In order to do this, I have to twist the center part (the nozzle) to face the flat part of the bottle. It doesn't leak. It works. I also find that the spring at the top combined with the nozzle inserted in the cage wire is sufficient to keep the bottle in place. I do not need to use the little metal piece that supports the bottom. I have a lot of rabbits & a variety of cages with different sized wire/spacing etc. I have not had any issues with using these bottles with any of my cages.After I fill the bottles I shake them a bit to knock the air bubbles out of the nozzle. Then I test it with my finger to make sure air bubbles go into the bottle & water is coming out. I do this for at least 30 seconds. If it doesn't seem to be working I just jostle it & test it again. Because the bottles are glass they don't suck in like they do when you handle a junky plastic bottle. So it is up to you to remove the air by giving it a shake. That's really all there is to it. A little common sense is all it takes. Watch out for the little yellow ducky, it can fall out of the bottle when you clean it. The little ducky is there for you to be able to tell at a glance how much water is in the bottle.*UPDATE* 2/12/15I still love these bottles. I have bought many more over the past year & a half. I have NO ISSUES! I have no idea why folks can't figure out how to make these work properly. They work fantastic! I will be buying more of them as some broke due to the cold weather (they froze because we left them outside too long it's been in the single digits to negatives so it takes very little time for them to freeze, we bring the bottles in & out all day long during this type of weather). These bottles are easy to use & easy to clean. I'm sick of plastic & thrilled to have these as an alternative.I plan to slowly replace all of my plastic water bottles with these wonderful glass bottles. I am doing everything I can to get plastic out of my life. I am a very happy customer!Love this water bottle. I use it all the time to supplement another larger Kaytee glass water bottle. I use it for rats.I got this one specifically because it is glass, which is highly unreactive and can be cleaned very easily, and because it is very small.I tend to clean it occasionally by soaking it in vinegar overnight and rinsing it in the morning. The sipper tube can also be soaked in a mug of vinegar overnight, to good effect.The only thing I don't like is how it attaches to the cage. There are two separate pieces which secure it to the cage, one of which is a long spring which attaches to the cage on either side of the water bottle. This is effective, but the spring is overly strong, and unhooking it requires a fair amount of effort ("potential energy"). The downside is that the spring will then BANG against the cage, and this scares the animals.This water bottle is well-designed and will work properly if the following are met:1). There is a Maximum Fill Line. Do not fill beyond this line, or the vacuum created will be too strong, and the liquid will not dispense. The operation of water bottles in general requires a significant amount of space above the liquid.This is not such a big problem for PLASTIC water bottles, which can flex slightly, but GLASS is rigid, and is very unforgiving when it comes to overfilling.2). The liquid should be at room temperature. If the liquid is colder than ambient, the bottle WILL leak until the liquid has warmed to room temperature. If the liquid is warmer than ambient, it will form a stronger vacuum as it cools, and may not dispense even if otherwise filled correctly.3). When unscrewing the top to fill/clean, apply torque ONLY to the plastic cap (underneath the chew guard). Do not untwist the cap using the sipper tube itself, because the cap wasn't meant to be unscrewed this way, and eventually this will weaken the watertight seal between the two, causing a leak.It leaks should have bought a 99 pence one off the market as it would have been better . Overnight the whole contents of the bottle empties into the cageBrilliant product, at affordable price.It is leacking . It is not good....Pues mira la solución esta en los comentarios de los gringos, es un buen producto pero por defectos de fabricación tiene fuga, la rosca que tiene por dentro tiene un tipo tapón hermético que se separa de la rosca principal, lo veras en su vista interna que mágicamente hace que no gotea, la SOLUCION ES CADA QUE HAGAS EL CAMBIO DE AGUA TIRA HACIA ATRAS EL PLASTICO PARA QUE QUEDE HERMETICO, todo lo demás es de buena calidad. sin no fuera por eso seria un producto de mega calidad.Our puppy had some surgery done a few months ago and this product has been a crated dogs life saver. Due to its longer spout it’s made it so much easier for her to drink water without the hassle of knocking over or pulling off the water bowls inside with her cone. And because it’s made of glass. She can’t chew it = BONUS!The only issue is sometimes the threads get tight after putting the spout lid on and it’s fairly hard to turn when trying to change the water due to not much grip to hold onto.