These molds are absolutely perfect for resin crafting and art projects. They are super easy to use, I don't need to sand after wards. I mix my resin in equal parts, I add any additives, then I pour resin, and lastly I spray with 91 percent alcohol. I haven't noticed any air bubbles. They make great gifts and perfect additions to your home decore. Crafter approved, five stars. Thank you so so so so so so much!