Owner's Acorn Floats are an excellent choice for fishing moving water. Their shape makes them very stable, which is wanted while fishing slightly turbulent water. The shape also makes them a much better choice than the Nakazima Ball Floats.
Spherical floats, like the Nakazima Ball Floats, Thingamabobbers or the familiar red and white bobbers we all used as kids will hold up a lot of weight. In reality, though, no one uses enough weight with them. To set a float properly, only a small amount of the float should remain above the surface of the water.
If a large percentage of the float's volume is above the surface, it takes a significant amount of force to pull the float under. Fish really will spit out bait if they feel tension on the line. Ideally, almost all the float should be under the surface. That makes the float very nearly neutrally buoyant, so only a very small pull from a fish will take the float under completely.
Floats for still water, like the Owner Top Floats, often have a very thin "bristle" sticking up from the body of the float. Enough weight is added to the line under the float so that only the bristle, or even just a portion of the bristle is above the surface. With only a bit of the bristle above the surface, the floats are almost completely neutrally bouyant, and very, very little force is required to take the float all the way under.
The Owner Top Floats are extremely sensitive, but are actually too sensitive for fishing in streams that have much current at all. The current at the surface is always faster than the current at the bottom. Rocks, logs or even just irregularities in the bottom slow the current. For an extremely sensitive float, even these small current differantials can pull the bristle under the surface. The shape of the Acorn Float makes it sensitive, but not THAT sensitive.
The stem and the rubber tubing makes them very easy to adjust. Thread your line through the tubing (before tying on your hook and attaching your split shot). Insert the float stem into the tubing, which will hold the float in place. To adjust the depth of your bait, pull out the stem, move the rubber tubing up or down the line and replace the stem.
The Owner Acorn Floats come in three sizes, 40mm, 45mm and 55mm (from the top of the float to the bottom of the stem. A couple years ago I carried the 55mm size, which is much better for trout in streams than for micros or even sunfish.
Currently, I have the 40mm size in stock, with the idea that they will be small enough to work well when fishing for larger micros (creek chubs, common shiners, etc.). Additionally, the smaller size should make them more appropriate for use with seiryu rods. When fishing for the smallest micros, I would still choose the Owner Tanago Floats, though.
The fluorescent orange top makes them quite visible, and the orange top is the only part of the float that should be above the surface. One Dinsmore BB shot will sink the 40mm float to the uppermost black line, leaving the entire orange top visible. Instead of one BB shot, you could use two #4 or four #6 shot (not counting the weight of your hook and bait). Test the float with the hook and bait you are using to get the proper weight. You might need a combination of #4, #6 and #10 shot to get the weight just right, so that only the orange top shows above the surface.