Filament diameter
Filament diameter is the thickness of the filament strand your printer melts and extrudes. The common sizes are 1.75 mm and 2.85 mm.
Why it matters
Your printer is built for one diameter. The extruder gears, the filament path and the hotend all assume it. The wrong size will not feed properly, so check your printer’s specifications before you buy.
Polymaker lists its PolyLite PLA in both 1.75 mm and 2.85 mm. Prusa lists its Prusament PLA at 1.75 mm for its FDM printers. Many printers take 1.75 mm, but always confirm for yours.
Consistency along the strand also matters. A thicker spot pushes in more plastic than the slicer expects, and a thinner spot pushes in less. Brands usually state a tolerance in millimetres on the product page. A tighter tolerance means a more even extrusion.
Diameter is a stated number, not a quality guarantee. Some product pages give no tolerance at all, so look for it before you compare brands.
When you compare spools, price per kg lets you ignore diameter in the maths, but not in compatibility. Our UAE filament prices and Saudi filament prices pages read the diameter from each listing.