United States military aviation insignia was going through quite a change during the early part of the US involvement in the Second World War in an effort to reduce the incidence of friendly fire. The insignia with the red border was one of the transitional patterns that was briefly adopted through 1943.

1/48 US national Insignia
Inside the resalable bag there are 34 masks of various sizes including:
-9 x 20˝ Insignia.
-7 x 25˝ Insignia.
-6 x 30˝ Insignia.
-6 x 35˝ Insignia.
-6 x 40˝ Insignia.
Also included are a number of strips that fill some of the spaces where there is not enough space to fit the insignia. These could be used for placing over the masks when transferring them to the model or if you have any left as wing walkways. The cover of the packaging states there is six of each size, but I suspect this is a miss print.
These masks are made from Kubaki tape, which seems to be the most popular media for mask making these days. It is very difficult to make out the individual masks on each sheet and impossible to photograph. The sizes are given on the mask, but they are a little tricky to see so take your time. The process is as follows:
The instructions are printed on the back of the label and to be honest take a bit of figuring out at first, but once understood seem pretty logical. It is claimed that the masks can be used several times and if so really makes good economic sense to use them if you are building a few US subjects from June to August 1943. Maketar idea of placing a strip of Tamiya tape along the centre line of the Insignia seems a very good one. This also keeps all the parts of the mask together and if placed correctly the tape will help to line the Insignia up correctly. Perhaps a tutorial on the Maketar website might be an idea, although they do offer help via email.

Price
Vinyl: £8.99
Kabuki: £9.79

NOTE the masks are also available in 1/72 & 1/32 scales.

Conclusions:

This will be an interesting method of achieving sympathetic looking marking for your models particularly if you like to weather your aircraft. The bright coloured decals always look at odds with heavily weathered paintwork. Just think no more decal solutions, silvering, annoying specks of dust and air bubbles under the decals spoiling your pride and joy. It may not be quite so instant, but the little extra effort involved using these masks could create that award winning model you have been dreaming about.