This is a much more extensive set of PE details for the Airfix F4F-4 kit, and actually includes both the larger sheet and the smaller #SS538 PE sheet which has the cockpit details. In addition, the much larger PE sheet provides parts to construct more detailed wings, including flaps and sections of the folded wings. Some of the inner details for the wings in the folded position are provided, and they look excellent. Also, a new firewall is provided, and some details for it. A set of bomb racks and shackles is also on the sheet. The parts are relatively easy to prepare for assembly, but some careful trimming is required, and I would suggest using some pretty sophisticated magnification equipment, as these parts are pretty small and assembly is tedious. If you want to display your model with the flaps in the “down” position, this set will fill the bill.
However, there is a major philosophical problem here. The PE SHEET provides two sets of flaps,