Leather Strap for WHOOP, Brown

The stainless steel frame is shaped to fit the WHOOP 5.0 sensor and holds both the standard version and the ECG version. The strap is not designed for older WHOOP generations, so before you buy, make sure yours is the fifth generation. The sensor is not included in the package: the frame takes the one you already use.

The outer side of the strap is brown with a fine grain texture, and a thin line runs along the edges. The inner side, which rests against your wrist, is smooth and light beige. The leather also covers the top of the sensor, so all you see on your wrist is a leather band in a matte stainless steel frame. If you knock your wrist against the edge of a desk or a door frame, it is the leather that rubs against it, not the sensor itself.

The strap is designed for wrists with a circumference of 180 to 210 mm. Seven holes divide the 30 mm range into six steps, so moving by one hole changes the circumference by about 5 mm on average. On a smaller wrist, the strap cannot be tightened enough and the sensor would shift, while on a wrist larger than 210 mm, you will not be able to fasten it. That is why you should measure your wrist with a soft tape measure before you buy, at the spot where you wear your WHOOP. When you wear the strap, choose the hole where it does not twist around your wrist but does not feel tight either.

The WHOOP sensor sits in a stainless steel frame that wraps around it from the sides and keeps it from shifting in the strap. The underside of the sensor stays exposed, so its optical sensing elements rest directly against your skin. Optical heart rate measurement is most reliable when the sensor does not move relative to your wrist, and the secure fit in the frame helps with that. Stainless steel also resists corrosion, so sweat and everyday contact with your skin do the frame no harm.