These fly boxes are made entirely out of EVA foam, so they will float if you drop them in the water. They have strong magnetic clasps, and most of the time I have dropped them, they close automatically before hitting the water or ground. This means you will not loose any flies due to clumbsiness. These fly boxes are large enough to hold medium to large streamers, and they are two sided so you can hold many flies in a small compact box. While this box can hold large flies, it also is small enough to fit in all fly bags Ive ever used. Including small chest packs. In fact you can usually fit multiple in a pack, allowing you to organize your boxes by fly type. These fly boxes are also very durable, and Ive had a few of them in rotation use over the past 6 years, and they are still in use. Ive never had them break or rip. These are my favorite boxes to hold small to medium streamers, and occasionally I will put large streamers in them as well. I regularly put flies (on both sides) that are tied on size 1/0 hooks, without any problems with them fitting. I use these for saltwater fishing down in the gulf for redfish with crab and shrimp flies, and also use these for bass flies when fishing my local waters where I use large poppers and streamers. When going out to fish for predatory trout, with large articulated streamers, these are the boxes I grab as well. Being made entirely out of foam, these fly boxes are extremely lightweight. This means your pack will not be weighed down by the box. They are just 2oz each fly box (before filling with flies). You wont even notice your fly bag is filled with fly boxes on long trips. Or just put in your pants pocket for short runs to the water, and you wont even feel them in there. This box holds up to 198 flies, less with larger sized flies. Flies not included