Rarity level 8/10❗️Authentic LEGO Bionicle exclusive White metal Krana Kal promo piece, also called WMKK. They're almost impossible to find these days and only 5000 have been produced + around 100 spares! :
LEGO part 42042Su - Pearl Very Light Gray Bionicle Krana Mask Su at BrickScout
LEGO part 42042Yo - Lime Bionicle Krana Mask Yo at BrickScout