This is a resin detail parts set for use with military vehicle kits.
Atak Model of Poland makes some of the best zimmerit sets in the world! What's zimmerit, you say? Why, it's that multi-patterned application of a paste-like material that was used by the Germans in WWII to thwart the attachment of magnetic mines to the metal hulls of tanks. The zimmerit itself was not anti-magnetic, as often erroneously reported, but simply non-magnetic, and functioned to hold the mines far enough off the hull so they would not attach magnetically.
One of the most difficult aspects of modeling German armor for many modelers is the complicated zimmerit application. It can be done by various methods, including the putty-and-razor saw (or zimmerit tool) method, the hot screwdriver method, or even the woodburning tool method (scary!), but none are easier or offer more realistic results than Atak Model's resin zimmerit sets. The sets include super-thin sheets of pre-formed zimmerit that you cut out with a modeling knife and apply to the model, plus larger cast resin pieces that completely replace some kit parts, such as mantlets, turrets, and other parts. Instructions are in English.
This set for the StuG III Ausf. G features zimmerit sheets, with resin cast hull parts, as shown below. For the Dragon and Revel StuG III Ausf. G kits.