I recently read that they do not keep them warm since torts have not body heat to keep in.
They actually keep them from getting light and warmth from exterior sources.
Fine for a photo session but not for clothing.
This. Bright colored yarn is much more visible than a camo tortoise. Some people also attach baloons to them.We have a member here, Katie, who makes these and some of them are so adorable. They are not made to keep the tortoise warm or even for them to wear all the time. They are used mainly to help keep an eye on your tortoise when they are out and about roaming around.