Quick question about my ex!

Hey guys! My partner and I broke up 2 weeks ago and after hanging out a few times I've told him I don't want to talk to him anymore as it's too painful. (He was the one who broke it off). I was cleaning my room today and decided I needed to give back the very expensive necklace he bought me... so I have parcelled it up and will post to him today... should I put a letter in the parcel at all? Or just send the necklace as is?