Answer:
The ERP records a red polypropylene co-polymer shell with triple corrugation and an extended nape. Karam lists ratchet-type adjustment and a protective peak.
The ERP product record identifies the shell as polypropylene co-polymer and notes triple corrugation, increased vertical clearance, and an extended nape. The Karam product page lists a protective peak, triple corrugation, and ratchet-type adjustment. The product shown here is the red PN521 variant.
