Although the outer packing was fine, inside they came in a very thin plastic bag - no plastic holder or anything. (amazon.co.uk)
Many plastic dog crates come in two pieces - a top and bottom - made of thin plastic material that are attached together with bolts. (topdogtips.com)
Use caution with thinner plastic containers — hot water can cause them to melt; and avoid glass — boiling water can cause glass to break. (scientificamerican.com)