Yes they are.

 

Plastic ones will usually strip and save your servo gears in a crash. I'm not a fan of alloy arms.

 

Alloy servo arms
A very good question
In the event of a crash the arm will not break is this a good thing or not?
Questions need to be asked such as:-
Are the servos plastic cased?
Are the servos hard mounted?
Have they got plastic gears?
Are any of the control levers plastic?
In the event of a mishap is it cheaper to replace the arm or another component?
Is there a possibility the plastic arm may fail during hard flight?
If the arm is soft will the control feel mushy?
The new generation high end servos are alloy cased, extremely fast, built with metal gears, generally survive the most severe mishaps provided they don’t stall and are normally fitted with metal arms.
Now choose!

 

Look nice . But destroyed 3 x bls451's in my gobby - never had it happen with plastic arms .

 

And the SAB servo arms seem quite nice.. I've got a set on the way...

 

In all 550, 600, 700, 800 helis I use alu arms. Never had problems. Maybe my cheap servos have stronger gears. For me plastic ball links break in case of crash. They work as fuse. I do not crash often. With bigger helis it happened few times but servos survived.

 

Hmmm , thanks for all your input and I've decided to put the alloy arms in and I agree that the ball links would be the weak link !

 

Do not take my advice for granted if you use fancy MKS, Torque etc. servos.

I am using TGY HV 1266 or 1267 (rebranded Power HD have titanium gears) of TGY MG HV BLS 815 and 805 (rebranded KST).

Those 815 and 805 are awesome. I crashed 800 nose in at full speed to the ground,(radio failure). I lost only main blades, 3 plastic ball links and mainshaft was slightly bent. All servos survived!

On the other hand I was able to stripp MKS DS-92 in 450 PRO in flight. MKS warns to not to use it in FBL. I was. I do not blame MKS. I still like DS-92.

Alu servo arms do not flex in flight (advwntage). If you crash often plastic arms can be good idea. I just do not trust plastic arms in 550 and bigger helis. New HV servos are really strong and cases of plastic ball links broken in flight are not rare.