It is difficult to close the lids. However, I noticed that they can be applied and closed relatively easily if they are placed with the side that has the top opening, on the side of the glass container that has the brand name letters.

Very good construction until... the sliding lids that the large plastic lids have for "ventilation" broke within 1 month, in the large and medium containers.

It is very good. The glass is of good quality and the lids have special silicone rubber to seal airtight. They also have a special hole for the microwave, which was initially difficult to find out if they fit or not, but I eventually found it in the instructions. The only downside is that they are quite small and the photo is misleading.