This item is called a tompion. The tompion was used to keep the rain,snow or mud out of the end of your musket barrel. These are made of wood and the end is slotted to allow the tompion to fit snug in the barrel, but still be able to pull it out if the wood swells.The tompion measures about 5" long. We strongly suggest that you only use this on an unloaded musket, as you would not want to forget and fire the musket with the tompion still in the barrel. We do not need any accidents, be safe when using these tompions. Just a note: some final fitting may be needed, such as a little sanding. We have found that not all barrels measure the same. Sometimes the tompion may fit tight and need sanded. Also have found that wood swells and shrinks, depending on the humidity. If the tompion fits loose, a wooden tooth pick inserted in the end will open the tompion to make it fit snug.