The Tecnifibre Duramix HD 1.25 tennis string offers ultimate durability combined with power & comfort. The string has a multifilament construction with a blend of polyester & polyamide filaments. The poly filaments provide superior durability. Replacing standard PU with a new high density PU offers enhanced performance. The string has a gauge of 17L (1.25mm) & the set provides 12m (40feet), which is enough to re-string one racket.