Wilson Combat Extension Tube Wave Washer for Remington 870

Hardened spring steel washer is specifically shaped to retain the late-model Remington 870 forend wood using the old-model magazine tube nuts. Allows you to install new model wood onto the older shotguns without having to drill the forend and stake in a magazine tube nut retaining detent.
 
This wave washer can also be used to help retain worn Remington 870 magazine tube nuts.