How many specifications and sizes of lean tubes are there?

The specifications and dimensions of lean tubes can be classified according to their materials, with the mainstream types as follows:

The standard outer diameter of steel-plastic composite lean tube is 27.8mm±0.2mm (often referred to as 28mm specification), with wall thicknesses covering 0.7mm, 0.8mm, 1.0mm, 1.2mm, 1.5mm, and 2.0mm. The conventional single length is 4 meters.
2. The mainstream outer diameter of stainless steel lean tubes is 28mm, with wall thicknesses of 0.8mm, 1.0mm, and 1.2mm. Some manufacturers also offer niche specifications of 19mm.
3. The standard specification for aluminum alloy lean tubes is 28mm, with 43mm used for high-load-bearing scenarios. A few manufacturers offer 19mm specifications. SUNQIT, a domestic company, has independently developed the 19mm series of lean tubes and corresponding connectors.