Seamless steel pipes have a variety of sizes and specifications. In order to meet the needs of different uses, there are usually multiple standard ranges in terms of outer diameter, wall thickness and length.

1. Common outer diameter range
Small diameter seamless steel pipe: outer diameter 6mm~89mm
Medium diameter seamless steel pipe: outer diameter 89mm~377mm
Large diameter seamless steel pipe: outer diameter 377mm~1200mm
Typical outer diameter size
Common outer diameters: 6mm, 10mm, 12mm, 25mm, 50mm, 76mm, 89mm, 108mm, 159mm, 219mm, 273mm, 325mm, 426mm, 530mm, 630mm, 720mm, 820mm, etc.

2. Common wall thickness range
Thin-walled pipe: wall thickness 0.5mm~4mm
Normal thickness pipe: wall thickness 4mm~25mm
Thick-walled pipe: wall thickness 25mm~100mm
Typical wall thickness specifications
Common wall thickness: 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm, 14mm, 20mm, 30mm, 50mm, etc.

3. Common length range
Ordinary length: 4m~12m (most common are 6m, 9m, 12m).
Fixed length: produced according to customer requirements, generally within 10m.
Non-fixed length: the length is not fixed, usually any length within 4m~12m.
Extra-long pipe: some special-purpose pipes can exceed 12m (such as pipes for oil pipelines).

4. Commonly used specifications combination
According to the purpose and standard, there are several common combinations of seamless steel pipe specifications:
Steel pipe for fluid transportation: outer diameter 20mm~530mm, wall thickness 2mm~50mm.
Seamless steel pipe for boiler: outer diameter 32mm~426mm, wall thickness 4mm~30mm.
Seamless steel pipe for high-pressure fertilizer equipment: outer diameter 48mm~325mm, wall thickness 4mm~40mm.
Seamless steel pipe for petroleum cracking: outer diameter 70mm~219mm, wall thickness 6mm~30mm.
Seamless steel pipe for structure: outer diameter 32mm~630mm, wall thickness 2mm~40mm.