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simple question on 5g servos

Why are 5g servos so much more "uncommon" than 9g servos? It seems I can find pages and pages of 9g servos to buy just about anywhere. Either individual or in bigger quantities. I would expect one could do the same with 5g servos (in theory it seems like a good option for lighter aircraft) but they just don't seem to be as plentiful. I have some 3.7g servos but wouldn't mind having some more 5g ones around too.
I did about 30 minutes of research and I didn't come up with much but Ill give you my first thoughts. I think the problem is manufacturing, I've heard 9gram servos referred to as the common size (maybe that's because they're the easiest to find, I'm not sure). Since 9grams seem to be the most common it's not cost-effective for all your brands to make the "uncommon" sizes. But you do end up being able to get some of the "uncommon" sizes because the bigger brands can afford to turn less profit on those servos because they are selling many other things as well.


Legendary member
I guess I can see how it happens, as far as supply and demand goes at least... If i want to build small, I get the smallest i can find. If I'm just doing a normal park sized build the weight isn't really as much of an issue so I'll use whatever servos I have laying around. Like you said, usually 9 gram...
Emax ES9051 is a digital servo listed at 4.3g for $4.50. They actually consistently weigh 4.8g, but I doubt that matters for what you’re doing. They’re well under two layers of DTFB thick and have been very reliable for me. I’m pretty sure FT rebrands these for a couple more bucks, but it doesn’t get much cheaper for digital 5g servos.
I've just noticed the same thing as I've started down the Mini path. I would like to save the weight and space with the 5g or even 3.7g but they are much harder to source and more expensive when I find them.


Building Fool-Flying Noob
Aliexpress has theme for around $2.7/ unit if you look around. I have found them to be not 100% functioning. so the per item cost tends to creep to $3. but still a 40% discount from $5per
3.7g: https://tinyurl.com/y8o94x7c
SG50s (~$3per): https://www.aliexpress.com/item/32937009729.html
I personally buy them in bulk when I can, so that I have an number ready for the next project. ) Know that isn't in everyone's abilities.


Master member
Heli max made a 1.5 gram for their mini helicopters, still available online here & there. Odd plug.
Bunch of 2+ gram linear actuator online fairly high torque. My issue is trying to actually see the bugger. Anything less than 5grams is impossible for me to deal with patiently.


Elite member
I am sure it is a case of supply and demand.
In the days before mini quads became so popular (no servos!) servos were readily available from China dirt cheap even the 3.7 g ones.
It appears only 9 g are used in quantity. Most cheap RTF planes use them.
With Covid 19 adding to the mix I suspect the days of super cheap RC bits are over. :(