T means Thread which is fiber, and the number reveals the sum of the vertical and horizontal fibers in a square inch of fabric (see photo). The larger the Thread, the denser the weave and the greater the durability of the fabric.

The waterproofing of a tent indicates how much water the outer fabric can repel. It is measured in millimeters (mm) and refers to how many millimeters of a vertical water column (and therefore pressure) a square centimeter of fabric can withstand without being penetrated by water.

The higher the degree of waterproofing, the less breathable the fabric is, and thus the warmer the tent. Common waterproofing values range from 500mm to 10000mm. Theoretically, any fabric with waterproofing >1000mm is considered waterproof. For example, a summer tent may have waterproofing from 500 to 1500mm.