Your axle dust cap is fitted to your axles brake drums which keeps debris away from your wheel bearing. Your caravan should have either an Al-Ko or Freedom axle fitted. This varies depending upon the year of manufacture.
If you are unsure which axle your Freedom will have, please send us an e-mail to spares@freedomcaravans.com with your chassis number, along with anything else you think may help such as images of the item you are looking to replace, and we will be happy to help.