Standard serves like mg90s. All gears are metal, but the output shaft rotates in a plastic casing, there is no bronze (or brass?) inserts. Some Serbs have a Luft output shaft (not very large, but still). Also in these Serva potentiometer in a green case, it seems more accurate and reliable. In general, normal inexpensive serves. The seller sent quickly, the track was tracked on the entire route.
Pretty good quality
10PCS FEICHAO Mini SG90 9g Micro Servo for RC Helicopter Airplane Car Boat MG90S Metal/SG90 Plastic Gear Micro Servo Optional
Super fast and product announcement.