From Fantasy Printshop, a line of roundels in 1/72 scale. This sheet is somewhat unique is that there is no clear varnish coating over the decals. This means that there is no worries about silvering of the clear film. It also means that one has to be a bit more cautious in handling these. The instructions state that these should be in water no longer than a second or two or they will curl. However, the end result will be well worth the additional handling precautions.

This particular sheet is for Type A roundels for mostly pre-WWII aircraft, though you would find this insignia on the underside of many early war aircraft. This one has the red and blue in a more subdued shade from the earlier roundels.   They come in three sizes on the sheet with those being 25, 35, and 45 inches in diameter. This should cover the vast majority of types then in service. The sheet is also available for 1/48 and 1/32 modelers.