Because adjustable bases move, you’ll want sheets that flex and stay put without bunching.

• Deep pockets and strong elastic: Look for 15–18 in. pockets (based on your mattress height) and all-around elastic for a snug hold.
• Flexible fabrics: Cotton percale feels crisp and breathable; sateen drapes smoothly; microfiber resists wrinkles; jersey knit stretches with movement; bamboo‑derived viscose can feel cool and soft.
• Split-friendly options: For split king or split-top (flex head) mattresses, choose sets designed for those formats.
• Smart details: Reinforced corners, corner/anchor straps, and head/foot labels can make fitting easier.

Matching the sheet’s size and pocket depth to your mattress can help reduce slipping as the bed articulates.

They’re made for different mattress setups.

• Split king: Typically includes two Twin XL fitted sheets (about 39 x 80 in. each), one king flat sheet, and pillowcases. Each side moves independently.
• Split top (flex head): Uses a single fitted sheet that’s partially split at the head so each sleeper can raise or lower their side while the foot remains connected.
• Split California king: Sized specifically for Cal‑king dimensions; it’s different from split king.

Check your mattress type (standard split, split top/flex head, or split California king) and depth before choosing. Product descriptions usually call out these formats to help you pick the right set.

A few small tweaks can help your fitted sheet stay in place as the head or foot raises.

• Match size and depth: Choose the correct format (e.g., Twin XL for split king) and pocket depth that fits your mattress, including toppers.
• Seek secure holds: All‑around elastic, reinforced corners, and built‑in corner/anchor straps can improve grip. Sheet suspenders or grippers are another option.
• Use a grippy base: A non‑slip mattress protector or pad can reduce shifting.
• Care matters: Wash before first use and avoid high heat, which may relax elastic over time.

These tips can reduce sliding for many setups, though results vary with fabric, mattress texture, and movement.

Most split king setups pair two mattresses side by side, so sheet sizing is a bit different.

• Fitted sheets: Use two Twin XL fitted sheets (about 39 x 80 in. each) so each side can move independently.
• Flat sheet: A standard king flat sheet typically covers both sides.
• Split top (flex head): If your mattress is connected at the foot but split only at the head, look for sheets labeled “top split” or “flex head.”
• Depth check: Confirm pocket depth against your mattress height, especially if you use a topper.

Always review product details for dimensions and compatibility to align with your specific base and mattress.

Pocket depth should match your mattress height so the sheet stays secure during movement.

• Measure first: Measure mattress height from base to top, including any topper or pad.
• General guide: Up to ~12 in. often works with standard pockets; ~13–15 in. benefits from deep pockets; ~16–18 in. may need extra‑deep pockets.
• Elastic matters: All‑around elastic and reinforced corners can help maintain a snug fit as the bed articulates.
• Fabric flexibility: Stretchy knits (like jersey) can accommodate rounded edges and slight variations in height.

Choosing the right pocket depth can reduce pop‑offs and bunching, but effectiveness can vary with fabric, mattress texture, and how often you adjust the bed.