The KST DS125MG Wing Servo is an amazingly good metal cased servo. It is exactly the same size and has 90% of the performance and build quality of the market leader, for less than half the price. Like the more expensive servo it has no geartrain slop.
At only 10mm thick this great wing-servo can easily fit in thin glider and jet wings. With a massive 7Kgf.cm torque the KST DS125 is appropriate for F3F, F3B, F3J, F5J, all fast gliders, and jets.  No longer supplied with metal output arms.