Hi I have a hs-81 mg micro servo, I need to know what size the screw is that is used to mount the horns to the servo. It is very small and seems to be a odd size. The screw backed out and I never could find it.

Part# 55802

I am not sure the size, but it is smaller than the standard 2.6mm ones.

2.3 x 5mm

Thank you, now I just need to find a screw a tad bit longer as I am installing this servo in my mini-lst.

I would try Micro Fasteners for a longer screw.
1-800-892-6917
www.microfasteners.com

microfasteners.com is a great place