33mm is about an inch.
< br >
The millimeter, also known as the millimeter (or millimeter), is a unit of length and a unit of rainfall, abbreviated mm.
< br >
10 mm is equivalent to 1 cm, 100 mm is equivalent to 1 decimeter, 1000 mm is equivalent to 1 meter (this is the meaning of the milli).
< br >
basic meaning
< br >
The abbreviation mm (or millimeter, also known as the millimeter (or millimeter), is a unit of length and a unit of rainfall, abbreviated mm (or millimeter). A millimeter is equivalent to one thousandth of a meter (this is the word milli).
The outer diameter 33 is a 1-inch pipe. 1 inch is the British standard, 1 inch is 25 points 4 mm, the international regulations of the pipe is represented by DN, followed by the metric diameter (approximate inner diameter) size indicates the size, the unit millimeter is not standard. In order to facilitate the unified use of all countries, the internal diameter of the 1-inch pipe is 25, the metric diameter is 25, and the outer diameter is 33.5 mm. When rolling, the wall thickness is allowed to be plus or minus 0.5 mm, and the diameter is 1 mm. So 33 outside diameter is a 1-inch pipe.