These are my favourite jars. I have now used over 400 of these jars and lids. I have not had one seal failure in over 600 uses. The jars are heavy and come well packed in environmentally friendly packaging. The lids are easy to replace; they take an 82mm lug lid.
This 500ml size is perfect as a meal for one or a part meal for two. You may find that for a single portion, 300ml is a better size, but it depends on your appetite. The 500ml is good for family sized jam.