Which preposition to use with penetrable

than Occurrences 1%

"I am armed with innocence, Less penetrable than the steel-ribbed coats That harness round thy warriors.

with Occurrences 1%

This case is easily penetrable with a knife, and is of pearly whiteness, more resembling cocoa-nut in appearance and texture than anything else I can compare it with.

Which preposition to use with  penetrable