Klean Shop Jam Jars With Lids – Red Lid Jam Jar Set – Fruit Mason Jar – Glass Jam Canning Jars – DIY 8oz (250ml), 24 Pack Jars- Perfect for Jam Storing, Pickles and Many Other

The concept of these jars is super cute but I'm really bummed out that they have these weird black pieces inside the glass. I have no idea what it is but it's obviously a defect.

I like the jars, but found that some are harder to take the seal when processed in the oven as I prefer to do.