From the end of 1941, the various roundel types used by the RAF began to be replaced by the compromise Type C design; this retained the classic red, white and blue colours, but with the white reduced to a very thin ring. This was used underneath the wings, and increasingly on top as well. (Although many squadrons kept the Type B on top until early 1945.) On the fuselage sides the Type C1 variant was normally used instead, which had an equally thin outer ring in yellow.
These decals are scaled to represent 30", 36" and 48" roundels in 1/300 scale. (They're also ideal for large aircraft in 1/600; equivalent to 60", 72" and 96" diameter.) The actual sizes are 2.5mm, 3mm and 4mm.