Flexfab 5521-025x800, 1/4" ID x 800 ft Spool Premium Green Silicone Heater Hose, 6mm 350F Radiator Coolant

Step up to higher pressure handling with the Flexfab 5521-025x800 premium silicone heater hose — a 800-foot spool of 1/4" ID hose with a thicker wall than standard heater hose. Its green-cover, red-liner silicone construction resists hardening, cracking, cold leaks, aging, and coolant-additive attack for dependable long-term sealing.

Why this Flexfab premium heater hose

• Thicker wall for higher pressure — 475 PSI burst rating, which means a wider margin over the ~158 PSI working pressure than standard heater hose offers.
• Silicone with 1-ply nylon reinforcement — superior flexibility with premium durability, extreme-duty-cycle tested for hostile engine bays.
• −65°F to +350°F range — holds up to under-hood heat and winter cold without going brittle or soft.
• Meets SAE J20 R3 Class A & TMC RP303B Class I Grade II — documented premium heater-hose spec.
• 1/4" (6mm) ID × 0.64" (16mm) OD, bend radius 5× ID — tight, kink-free routing.

Supplied as a continuous 800-foot spool, ideal for heater core, radiator, and coolant runs that need extra pressure margin. Pairs with a Flexfab 2582-0006 clamp. (Silicone heater hose is for coolant/heater use — not fuel.)

Backed by hpcouplers’ fast shipping and easy returns — order with confidence from a trusted industrial hose and coupler supplier.

• FlexFab Series: 5521
• Part Number: 5521-025x800
• Inside Diameter (ID): 0.25" (6mm)
• Outside Diameter (OD): 0.64" (16mm)
• Overall Length: 800 feet (Spool)
• Wall Thickness: .170" / .220"
• Weight LB/FT: 0.121
• Actual Burst Pressure - PSI: 475
• SAE J20 R3 Class A - PSI: 475
• TMC RP303B Class I Grade II - PSI: 125
• Bend Radius: 5x ID
• Extreme temp range: -65F to +350F
• Construction: Green cover / red liner Silicone hose with 1-ply nylon fiber reinforcement