The UPU option comprises of the classic/old Post services most countries have. I introduced it as an option for shipping because some clients advised that, for various reasons, they would prefer that service.
You are responsible for paying any fees when these products enter your country. Some names I heard of are: customs fees, duties, taxes, handling fees. These depend on the regulations of each country and I can't possibly advise you on it. If you think they may be a concern, please check with your Customs. Usually they have that info on their website.