Hi Carolyn,
If you are using the PIRF-100 Indoor Barrier the collars listed below will work with it.
https://www.radiofence.com/petsafe-deluxe-ultralight-dog-fence-collar
https://www.radiofence.com/petsafe-deluxe-small-dog-pet-fence-collar
https://www.radiofence.com/petsafe-stubborn-dog-collar
https://www.radiofence.com/sportdog-underground-dog-fence-collar
https://www.radiofence.com/petsafe-deluxe-ultralight-collar-refurb
https://www.radiofence.com/petsafe-cat-fence-collar