What are these grey scoop-shaped parts with a hole for an axle? I got these in a lot that I bought and I have no idea how to identify them. They have dates from 05 and 02, but no part numbers.
This is: 

Part# 42042 : Light Gray Bionicle Krana Holder 3 x 4

Keyword: 3 x 4, Color: Light Gray

it appears in 13 sets