A serger needs two different threads doing two different jobs, and this pack is simply both of them in one color. Four spools: two of SoftLoc™ Tex 35 wooly polyester for the loopers, two of Designer™ 40wt all-purpose polyester for the needle.

SoftLoc is the fluffy one. It spreads out to fill an edge, which is what makes a rolled hem look solid instead of gappy, and it's soft enough to sit against skin on knitwear. Designer is the workhorse — 40wt general-purpose polyester rated to 50 lb per inch of seam strength, so it holds a garment together and runs clean at serger speed.

Buying them matched saves the usual annoyance of hunting down a wooly poly that actually agrees with your needle thread.

White is the default for light fabrics, and the one most people run out of first.

Details

• Contents: 4 spools — 2 × SoftLoc™ Tex 35 wooly polyester, 2 × Designer™ 40wt all-purpose polyester
• Colors: matched across all four spools
• SoftLoc goes in: upper and lower loopers — rolled hems, decorative edging on medium to heavy knits and wovens
• Designer goes in: the needle, loopers, garment construction and general sewing; also fine on a domestic machine
• Seam strength: up to 50 lb per inch (Designer)