Heres a reference table for folks.
Ace/Thunder: 25T
Airtronics: 23T
Blue Bird: 25T
Cirrus: 25T
Duratrax: 25T
Futaba: 25T
Hitec: 24T
Hobbico: 25T (Some servos like the CS-170 uses 24 splines)
HPI: 25T
Jr: 23T
KO: 23T
MRC: 23T
Multiplex: 23T
Power HD: 25T
Sanwa: 23T
Savox: 25T
Spektrum: 23T
Tamiya: 25T
Team Associated: 25T
Tekin: 25T
Tower: 25T
Traxxas: 25T
Xpert: 25T
Losi: 25T