It is not a bubble per say so much as what is called an adjust a bubble. It can be filled with water or used as a float, it has a piece of rubber tube that goes through the middle so you can either use it so it does or does not slide. I prefer it for several reasons but I will give you a few. First of all the large one, when filled with water, is about a half ounce casting weight until it hits the water then it is only the weight of the plastic bobber and it sinks slowly compared to a barrel weight. Second if you cast into the weeds with it then it hangs up higher off the bottom and you are using floating bait it will put your bait up in sight of the fish where the fish can see it vs being hidden in the weeds where the fish has to find it by scent. Next when you have a fish on there is virtually no weight for the fish to have to battle..lead weights will go to the bottom of the weeds and pull your weight with it and out of sight. I put my bubble above my snap swivel and change the length of leader in relation to the depth of the water. If I am under 8-10 ft I use about a 1 1/2 to 2 ft leader and if I am in 20 ft I use 4 to 5 ft and anything deeper I adjust according to where the fish are holding. Trout, like salmon and other predatory fish can look up easily but they cannot look down as easily. So I use the combination of the bubble and leader to put my bait about in the middle of where the fish are holding, since they look up to take their prey my bait is in sight of more of the fish than it would be if I fished close to the bottom. I also sharpen my hooks, yes even new ones, and I use a single egg hook unless they are really biting light and then I use a small treble. I only use enough bait on to cover the hook. To much bait and the hook will slide out and leave you fish-less. I have been using this system for about 15 years now and my shortest time for 2 5 fish limits at Diamond is 1 hour. My best day with this system using 2 poles on average but for a while we had 4 poles out, till it started snowing and at that time we reduced to 2 poles but we did 42 fish that day in about 5 hrs. Oh there is one other thing that you may want to know if you go to this system, you will need to leave a belly in your line as you cannot have a tight line and then another is DON'T SET THE HOOK, that's right don't set it, let the fish do that for you. When the fish hits you pole and trys to DRAG you pole over the side the second time well all you have to do is reel in the fish as it will most likely be hook in the throat. If you don't want the fish then leave it in the water and cut the line unless the fish is bleeding, if it is bleeding you may as well keep it cause it will die anyway. I have not set a hook since I started using this technique, I have taught it to a a decent share of people and they all have usually increased their catch rate. When my son remarried a few years ago his step son was about 5 when we took him to diamond, used this method and the poor little guy reeled in 16 of the 18 fish we caught that day and a few times we had on two fish at a time with four poles and once we had three fish on. I hope you can read my poor typing, but that is why....a little long winded......sorry. If a five year old can catch fish using this method....well. Oh ya you may want to learn how to do a fish dance just in case.