Hohrein .22 caliber conversion kit

I used this kit make by Jonathan Arthur Ciener Inc. to allow my Ruger Mini-14 to shoot .22 LR ammo. It also functioned in my full automatic AC-566. I sold the rifles some years back and have no use for the sub-caliber reducer.

My questions are , what's it worth? end more importantly, what do I list it under and how best to describe it?

Would appreciate any advise.

Thanks,

Tennessee.Traveler