How It Works: Air is taken up by the fans through your sheets and comforter as in the diagram above. Topper will hang approx 0.5 inches off the foot of your mattress. Air is circulated through the whole topper from head to toe at optimal pressure for cooling according to automatic temperature adjustments and chosen set point. (Manual control touch-operated through fitted sheet - no need to pull it back) Dual Zones Width Length Thickness Mass Queen 151 cm / 59.5” 202 cm / 79.5” 5 cm / 2” 16 kg / 35 lb King 192 cm / 75.5” 202 cm / 79.5” 5 cm / 2” 23 kg / 50 lb Split King* 192 cm / 75.5” 202 cm / 79.5” 5 cm / 2” 23 kg / 50 lb California King 183 cm / 72” 212 cm / 83.5” 5 cm / 2” 23 kg / 50 lb *Split King purchasers are sent both a Twin XL and Twin XL-Left topperFor Dual Zones. . .- Each sleeper can use their own phone/tablet and manual controls - Single Sleepers will experienced reduced thermal performance sleeping in the center of a dual zone Smart Topper.Single Zones Single Zones Width Length Thickness Mass Twin 97 cm / 38.5” 189 cm / 74.5” 5 cm / 2” 10.5 kg / 22 lb Twin XL 97 cm / 38.5” 202 cm / 79.5” 5 cm / 2” 11 kg / 24 lb Twin XL-Left 97 cm / 38.5” 202 cm / 79.5” 5 cm / 2” 11 kg / 24 lb Full / Double 134 cm / 53" 189 cm / 74.5" 5 cm / 2” 14 kg / 30 lb For Single Zones. . . - One sleep zone intended for one sleeper- Single manual controller on Right Side as pictured above- Only Twin XL-Left has the controller located on the left side of the Smart Topper NOTE: If you are purchasing a Twin XL for one half of a King bed, it's extra important that the manual controller is on the correct side (not in the center of the bed!)