Great extender band for fitbit charge, fitbit charge hr, fitbit charge series 2 3 4 5, fitbit versa and fitbit versa 2 watch bands. Use as simply as the way like you wearing wristband - just simply keep the buckle locking the extender on one end and the extender buckle the band on other end, then you "create" a larger wristband! Connecting with our extender band, you can easily extend the wristband from small size to large size even x-large size, if you like, you can also put the wristband on your ankle and you are able to get more accurate steps when cycling, running on a treadmill, or pushing a grocery cart, etc.