Split King Flannel Sheet Set Dark Blue - 100% Cotton Velvety Soft

Our review of the Split King Flannel Sheet Set in dark blue finds it best suited for anyone who wants a warm, heavyweight cotton option for cold months and needs a split king fit. The set includes two Twin XL fitted sheets with deep 15-pocket construction, a king flat sheet and two king pillowcases, so it is a practical choice for adjustable mattress bases that use two mattresses. The single biggest reason to buy is the thick, tightly woven double brushed flannel that delivers noticeable softness and warmth while remaining breathable and naturally wicking.

Key Features

• Complete split king bundle: Two Twin XL fitted sheets, one King flat sheet and two King pillowcases provide a full bedding solution for split king beds.
• Deep pocket fit: The fitted sheets have 15 deep pockets and are sized 39 x 80 in to securely wrap deep mattresses without slipping.
• Velvety heavyweight flannel: The double brushed construction gives a plush, dense surface that holds warmth on cold nights while feeling soft against skin.
• 100% cotton construction: Being cotton means the fabric is breathable, hypoallergenic and naturally wicking rather than synthetic.
• Easy care: Tightly stitched seams and strong fabric mean the set can be machine washed on a gentle, cold cycle without special handling.

Who It's For

This set is a clear fit for sleepers with split king adjustable bases or two-twin-XL configurations who want a warm, natural cotton flannel that feels plush and sleeps cozy in winter. It also suits buyers who prioritize OEKO-TEX STANDARD 100 tested textiles and prefer products that are microplastic-free and net carbon negative.

Shoppers who need lightweight cooling sheets for hot climates or those strictly wanting zero pilling long term may want to consider other options, since a number of users report pilling starting after the first few washes despite the initial softness and quality feel.

Pros & Cons

Pros

• Thick, plush flannel offers immediate and lasting warmth for cold-weather sleep.
• The split king bundle includes two deep-pocket fitted sheets for secure fit on tall mattresses.
• Made from 100% cotton and OEKO-TEX certified for hypoallergenic, breathable comfort.
• Good value given the heavyweight feel and complete set of pieces included.

Cons

• Some customers report pilling after washing, which can affect surface smoothness over time.

Specifications

Included pieces	Two Twin XL fitted sheets, one King flat sheet, two King pillowcases
Fitted sheet size	39 x 80 in with 15 deep pockets
Flat sheet size	102 x 108 in
Pillowcase size	20 x 40 in (King)
Material	100% cotton double brushed flannel
Care	Machine wash cold on gentle cycle
Certifications	OEKO-TEX STANDARD 100

Our Verdict

The Split King Flannel Sheet Set in dark blue is a solid buy for cold-season sleepers who need a split king configuration and want a plush, natural cotton flannel that holds heat well. It delivers strong initial softness, a secure deep-pocket fit and responsible certifications, making it good value for the price; just be aware that pilling is reported by some users after washing.

Frequently Asked Questions

Do these sheets fit deep mattresses?
Yes, the fitted sheets are Twin XL sized at 39 x 80 in and feature 15 deep pockets designed to fit taller mattresses securely.

Are the sheets machine washable?
Yes, the fabric is tightly stitched for durability and can be machine washed on a cold, gentle cycle.

Will these sheets keep me warm without overheating?
The heavyweight double brushed 100% cotton flannel is designed to retain warmth while remaining breathable and naturally wicking to help regulate temperature.