Sei Sheet Set

The Sei Sheet Set is 100% long-staple cotton in a sateen weave, with a 600 thread count. That is the highest thread count MATTEO produces. At 600 TC, the fabric reaches the upper limit of what a sateen weave can do before density starts to work against softness and breathability. The result is a silky, fluid hand feel with a distinct face-to-back contrast characteristic of true sateen construction.

Thread count measures weave density, specifically how many yarns fit in one square inch of fabric. It does not measure cotton quality, yarn smoothness, or weave balance. Sheets marketed above 600 TC typically achieve that number through multi-ply yarns, which adds bulk without adding softness. MATTEO caps Sei at 600 TC because going higher produces a stiffer, less breathable fabric. The quality of the raw cotton and the garment-washing process contribute as much to how the sheet feels as the thread count itself.

Each Sei Sheet Set includes one fitted sheet, one flat sheet, and either one or two pillowcases depending on size. King and Cal King sets include two King pillowcase singles. Queen sets include two Queen pillowcase singles. Full sets include two Queen pillowcase singles with a Full fitted sheet and a Queen flat sheet. Twin and Twin XL sets each include one Queen pillowcase single. To mix colors across pieces, order each item separately.

Sei is 100% cotton sateen with no synthetic fibers, dyed using non-toxic reactive dyes. The sateen weave puts the smoothest face of the fabric against the skin, which reduces surface friction compared to a percale or plain weave. The garment-washing process used at MATTEO pre-softens the fabric before it reaches you, so there is no stiff break-in period. There are no harsh finishes or chemical whitening agents in the Sei collection.

Garment dyeing means the finished product is dyed as a whole rather than dyeing the yarn or fabric before construction. This process gives Sei its distinctive depth of color and a lived-in quality from the first night. Because it is an artisanal process, MATTEO allows for a shade variation of +/- 10% from dye lot to dye lot, and reactive dyes are used throughout. All items in a single sheet set order are dyed together to ensure color consistency within the set. Learn more about MATTEO's garment-dyeing process.

Wash in lukewarm water with a gentle detergent and a cool rinse, separating light and dark colors. Do not use bleach or products containing chlorine, alpha hydroxy acids, or benzoyl peroxide; the reactive dyes used in garment dyeing are not resistant to whitening agents. Tumble dry on low heat and remove the sheets promptly to reduce wrinkling. Line drying gives the best results and extends the life of the fabric.

The Sei Sheet Set is a considered gift for anyone who sleeps on 100% long-staple cotton. At 600 thread count with a sateen weave and garment-dyed finish, it reads as a complete, ready-to-use luxury bedding set rather than a single piece. The color range, which runs from Greige and Off White through Fig, Coal, and Iris, gives registry shoppers clear choices that work across a range of bedroom aesthetics. Designed and manufactured by MATTEO in Los Angeles, each set arrives with the full material story intact.

The Sei Sheet Set is 600 thread count 100% long-staple cotton sateen, which meets or exceeds the specifications used in high-end hotel bedding programs. Hotels in the luxury tier typically use sateen-weave cotton in the 300 to 600 TC range for its smooth drape and durability through repeated washing. Sei is designed and manufactured by MATTEO in Los Angeles, with garment dyeing and non-toxic finishing that go beyond standard hotel supply-chain specifications.