Smooth-wall design. Tight, leak-resistant seal protects contents from contamination and helps prevent messy leaks and spills. Exceptional temperature resilience enables use in freezers, refrigerators and microwaves. 33test33 Smooth-wall design. Tight, leak-resistant seal protects contents from contamination and helps prevent messy leaks and spills. Exceptional temperature resilience enables use in freezers, refrigerators and microwaves.