Mack 4379-RD109580 Heater Core PAI 804059CROSS REFERENCE: 4379 RD109580 APPLICATION: Mack R RB RD RW DM Multiple Use Application. APLICATION: Red Dot System BRAND: PAI 804059 Mack 4379 RD109580 Heater Core PAI 804059. Heavy duty parts and heavy duty. Supports consistent heat transfer and ensures stable interior comfort. All components are proudly manufactured in the U. S. A. by PAI Industries Inc., an ISO9001 certified company with over 50 years of experience in the heavy duty truck parts