Which is the oil mouth of the dental high-speed handpiece?

I wonder if your dental high-speed handpiece is a few holes. If is four holes of the mobile phone, it is the second largest oil tube, if is two hole, is the largest oil tube, because the two pipe inlet pipe, this is from the air inlet pipe, oil filled mobile bearing can obtain the lubrication, the end of the handle, in the mouth of the joints of dental chair.