Quick email I received from a plastics manufacturer.

I asked if a particular product was blow molded or roto molded. Answer:

“My guess is blow molding …, but the [product material] description [says] ‘vinyl’ which means [it must be] roto molding.   If it is blow molding, the product will be quite hard because HIPS or ABS material will be used.”

Side note from me:

ABS is acrylonitrile butadiene styrene, an oil-based plastic. It is technically grouped under #7 plastics. Generally, if we remember from an older post, #7s may or may not be safe. And may or may not be recyclable. But, ABS is one of the good #7s (NOT PC) as it has been  found to be stable and non-leaching. Legos are made out of ABS (though they are starting to think about moving away from ABS).

HIPS is High Impact Polystyrene. More on HIPS here. I think high impact polystyrene is a subset of just the #6 polystyrene plastics, which we have labeled as an Avoid plastic because of its possible carcinogenic qualities.