Put them in a light weight carton, some light weight bubble or crushed paper padding, for under $6 -- First Class Package rate. If over 1 pound, send it Parcels Ground rate -- somewhat more, depends on location ("zone"). These are "Retail" rates, cheaper if you print your own shipping-postage labels ("Commercial" rate).

Rates here. Bookmark it -- "good old" Notice 123:
https://pe.usps.com/cpim/ftp/manuals/dmm300/Notice123.pdf

Robert