Polyester is available in many different thicknesses, including 300 denier and 600 denier. Three hundred denier polyester is a lightweight fabric, whereas 600 denier polyester is more heavy duty. Each fabric has its own merits and can be used in different situations.
Terminology
Denier is a unit of measurement used to quantify the thickness of yarn. Denier can also be used to describe the overall thickness of a fabric, as this is an extension of the thickness of the yarn used in the fabric. It is abbreviated as the letter "D" after the number. The higher the number, the thicker the fabric will be.
Advantages of 300 Denier Polyester
Three hundred denier polyester is a thinner fabric than 600D. This fabric is more lightweight and smoother in appearance. Typically it will be less expensive than the more heavy duty fabric. It is used commercially in lightweight backpacks, electronics accessory cases and inexpensive luggage.
Advantages of 600 Denier Polyester
Six hundred denier polyester is a heavy duty fabric. It is used in high quality backpacks, rugged computer cases and luggage. This material is twice as thick as 300D poly. It is more durable, but more expensive.