These accessories are manufactured by Quickboost to provide additional detail to currently produced models. In this case, the accessory kit consists of two parts, a resin casting of the mechanical compass located behind the gunner’s position on the JU-87D, along with a clear plastic cover which fits over the unit to protect it from the elements.
From the photos I have examined, these compasses are not prominent features of the airplanes and don’t show up on many photos. When the gunner’s canopy is slid back, the unit would be invisible underneath the canopy. Nevertheless, they generally were installed, similar to those on the JU-88, which are depicted on some of the better JU-88 kits. None, to my knowledge, appears on any JU-87D/G kit. Therefore, this unit would be useful on any of the late-model Stuka kits, whether they be Fujimi, Academy, Revell, or even the old Frog kit. A scale drawing of the exact location is provided in the instruction sheet.