This 18th century accessory is for cleaning your musket in the authentic way using tow. Button jags were not common in the historic time period, so tow, a by-product of manufacturing linen, was used to scour the bore. This worm threads onto a steel rammer and the tow is wrapped around it.
This worm can also be used to retrieve a lost cleaning patch from the bore should you lose one off of a button jag.
Please specifiy what model gun you want the worm to fit so we can be sure it has the correct threads.