Good evening together,
the dimensions on the german JR-Homepage for the named servo are not correct.
The JR SLS 01 is a Standard-Servo with a case in 41x21 mm² dimensions. The center of the holes for fastening the servo measure in at 50x11 mm².
What makes the difference to many other servos is the height of the case. There are only 20,5 mm under the fastening plate. A modern name for that is "Low-Profile".
Hope that helps.
Gruß, Wolfram