# Servo horn dimensions - What is 25T?

I wonder that horns for servos are marked in some T units. Example: 25T

• What are the differences between H25T spline and 25T spline? They are different. Aug 27 '21 at 11:45

The T indicates the number of teeth or ridges in the servo spline. You need to match the servo spline to any device splines or they won't mate.
• Are those teeth have some standard dimensions? Ex, pitch 2mm and pitch 1mm are comletely different cogwheels Oct 15 '20 at 16:13
• @filimonic - Kind of. You need to make sure the ratings match; here's a link that shows different splines. So a servo like this is advertised as a "25T" spline, but the earlier link shows that there could be a B25T or H25T spline, so you need to look further at the datasheet. The product page shows, under the SPECS section, 25 tooth (H25T Spline) spline - so it's an H25T standard spline. B25T splines are not compatible. Hope this helps. Oct 15 '20 at 17:23