Check out these super cool pop tubes. They come in four bright colors and make amazing sounds. Thus our warning that these are not for quiet areas. Simply pull both ends to make the tube expand then compress the tube to make a really neat sound almost like water filling the tube. With supervision, you can even twirl them over your head to make a whistling sound. These sound tubes are really fun and would be great for audible stimulation. They measure about nine inches and stretch to over two and a half feet. You can also connect the tubes to each to make shapes.