3mm is almost a 8 gauge earring. the tail goes through the ear hole for the seahorse to dangle.
Not made to stretch ears or to leave them in the ear for long periods of time. If irritation happens remove the earring and consult a physician.
You could put a clear coat spray on the piece to protect your skin from the plastic.
Keep them clean by water and mild soap. do not submerge. suggested not to shower with. Water may get inside, make sure it drys completely.
Strong and Flexible plastic is dishwasher safe, not watertight, not recyclable, and not food safe. Strong & Flexible plastics are heatproof to 80℃ / 176℉ degrees. Higher temperatures may significantly change material properties.