A single pipe hole mini water pump is a type of mini water pump that is designed to be mounted on a single pipe or tubing, typically with a diameter of 1 inch or less. These pumps are commonly used in applications such as aquariums, fountains, and hydroponic systems. Transparent Water pipe for 6v Submersible Water pump. Fits tightly on the 6v Submersible water pump that has a 6mm outer diameter. The pipe is slightly flexible and sturdy it is good for fitting it on the pump.