Sei Flat Sheet

The Sei Flat Sheet is 100% cotton, woven in a sateen weave at 600 thread count. It uses a 120/2 Ne yarn in both warp and weft, which gives the fabric a balanced, silky hand on the face side. At MATTEO, 600 TC is the ceiling we work within because counts above that tend to produce a stiff, dense fabric that does not breathe well. Thread count measures only weave density; yarn quality and weave balance are equally important factors in how a sheet actually feels.

Thread count is one measurement of weave density, not the full picture of sheet quality. A square inch of fabric cut from a 600 TC sheet has 600 individual yarns, but that number tells you nothing about the softness of the raw cotton, the smoothness of the yarn, or the balance of the weave. Focusing only on thread count is similar to choosing a wine by alcohol percentage alone. The Sei fabric is woven from 120/2 Ne yarn in both directions, which produces the silky, even hand that makes this sheet stand out among high thread count cotton sheets.

The Sei Flat Sheet is available in Twin (79 x 106 inches), Queen (100 x 111 inches), and King (118 x 111 inches). For a California King bed, order the King flat sheet. For a Full bed, the Queen flat sheet is the right fit. These are the finished, garment-washed dimensions.

Wash light and dark colors separately in a lukewarm cycle with a gentle detergent and a cool rinse. Do not overload the machine, as this can damage the long cotton fibers. Tumble dry on low heat and remove promptly to reduce wrinkling; line drying gives the best results. Bleach is safe on white cotton only. For garment-dyed colors, avoid chlorine bleach, alpha hydroxy acids, and benzoyl peroxide, as the reactive dyes used in garment-dyeing are not resistant to those whitening agents.

Garment-washing is a finishing process applied to the Sei fabric after the sheet is cut and sewn, rather than washing the raw yardage before construction. This process sets the color and gives the sheet a broken-in hand from the first use. For garment-dyed colors, the reactive dyes used produce a lived-in depth of tone. Because dyeing at this stage is an art rather than a precise science, a shade variation of plus or minus 10 percent between dye lots is normal and expected. You can learn more about the garment-dyeing process at MATTEO.

Sei is a sateen-weave sheet, which means the face of the fabric has a soft, smooth finish and a subtle sheen; percale uses a one-over-one-under weave that gives a matte, crisper hand. Sei's 600 thread count and 120/2 Ne yarn produce a denser, silkier surface than most percale offerings. Sateen at this weight is well suited to year-round use and tends to feel heavier and warmer against the skin than a comparable percale. Shoppers who prefer a light, breathable sheet may want to consider MATTEO's broader sateen collection alongside our linen options to find the right fit.

The Sei Flat Sheet is 100% cotton with no synthetic blends, and MATTEO uses non-toxic dyes in its garment-dyeing process. The 600 thread count sateen weave has a smooth face that does not have the coarser texture of lower thread count or rough-finished cottons. For those with sensitive skin who prefer a pre-softened sheet, the garment-washing process means the fabric arrives ready to use without a stiff, unwashed feel. White and Off White colorways are undyed and the safest option for those with dye sensitivities.

The Sei Flat Sheet has a 1/2-inch hem finished with a double stitch detail. On darker colorways, the top stitch is a contrasting white, which adds a visible tailoring detail at the fold. The sheet is designed and manufactured by MATTEO in Los Angeles. It pairs directly with the Sei Fitted Sheet and is part of the full Sei Fabric Collection.