Our Tab-Chek™ Check valves are an adhesive strip with a soft seal center, they are placed over the hole and centered, as the Pump-N-Seal® pumps air out the patented Tab-Chek™ keeps air from coming back in, it seals airtight, allowing your jar or container to be strongly and dependably vacuum sealed. You can reseal your container 100’s of times using the same Tab-Chek™ valve!