Made by Servorahmen to give a neat easy fit and finish into solid core models such as the Samba Prestige and others. Once holes are made for pushrods and leads in the cores, these frames drop straight in.
IDS Foam frames have a bottom to them so the servo is raised up by approx 0.5mm making the total installation 10.5mm but it makes them simpler to fit as no glue can get to the servo. Also the increased thickness has allowed the C507/X08 frame to have a ballrace rather than the plastic bushing.
Price is for 1 frame