Mammal: up to 500gr
Small Bats use Glued units or Backpacks with one hole so a thread can go around the neck and then are also glued. Larger bats can use Collars. Bats are considered to be able to carry up to 5% of their own weight. The length of time that glued units will remain on the animal before falling off depends on the environment (humidity, temperature) and type of glue used (up to 3 months because of hair growth).
Collars are the best option for small mammals like rats, mice, squirrels, etc. Glued options are used for the smallest species because these are the lightest possible units, or also when it is desired to recover the transmitter after an estimated period of time (less than 3 months).