Pneumatic Servos are crafting materials added by Thermal Expansion. They are commonly used to craft devices that do not require Redstone Flux to operate.
This item used to be required to enable Itemducts to pull items out of inventories without receiving a Redstone signal. However, this is no longer the case; Servos now serve this purpose.
If enabled in the config, Pneumatic Servos may also be crafted using Silver, Bronze, Invar or Steel Ingots instead of Iron Ingots.