These watch bands fit perfectly on my fitness tracker. I suppose it's to be expected that the band will become loose over time, since you have to remove the band to charge the tracker. But these are a good value for the money and so far are holding up better than the original band!
[5 of 5 Stars!] 
Vornado Lucerna 3 Alchemy Ultrasonic Humidifier - Amber 
Samsung Galaxy A20S (A207M/DS) 32GB + 3GB RAM 6.5" Display, Snapdragon 450, 4000mAh Battery, US & Global 4G LTE GSM Unlocked - International Model 