How do those little crisping sleeves that come with hot pockets and other microwaveable foods work?

Question

How do they make it so crispy?

Answer 1

They are 'reflective' so that the 'microwaves' bounce back' onto the outer edge of the item inside, which helps 'dry them out' and turn them 'brown and crispy.'

Answer 2

it is like a minute amount of metal that those crisping sleeves, microwave popcorn bags, and anything else have to do the crisping but doesn't make the microwave blow up.