What material are your custom in-ears made of? Follow Our custom shells are made of hard acrylic plastic. It’s durable, hypoallergenic and easy to clean. Related articles How long does it take to manufacture UE Pro Custom In-Ear Monitors? What is IPX technology? Does Ultimate Ears Pro keep my ear impressions or send them back with the order? Do you have a contact number? Do you offer custom artwork? Which format do you require?