These are replacement body O-rings for DIG Hose Thread Filters.
If the body of the filter leaks where the two halves connect check the body O-ring for damage. The O-ring should be removed, cleaned and inspected periodically. If dry, it should be lubed with O-ring lubricant (HLUBE). If damaged, it should be replaced. O-ring lubricant will prolong the lifespan of O-rings and help create a watertight seal.