Great question, Lin. This product is not designed to repel fleas. – Elizabeth, SC Johnson Consumer Care
The gray top part should twist so you can pull out the filter and insert the new one.
Hi Bait55. The OFF! Clip-On Mosquito Repellent Starter refill can be found at your local Home Depot Store. It is located right next to the OFF clip on Mosquito Repellent kit. This should be located in the Garden Department your Home Depot. Please let us know if we can be of further assistance. Rick_HD_OC