Flexfab 5521-100x25, 1" ID x 25 ft Box Premium Green Silicone Heater Hose, 25mm 350F Radiator Coolant

Step up to higher pressure handling with the Flexfab 5521-100x25 premium silicone heater hose — a 25-foot box of 1" 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 — 300 PSI burst rating, which means a wider margin over the ~100 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" (25mm) ID × 1.39" (35mm) OD, bend radius 5× ID — tight, kink-free routing.

Supplied as a continuous 25-foot box, ideal for heater core, radiator, and coolant runs that need extra pressure margin. Pairs with a Flexfab 2582-0016 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: 5521-100x25
• Inside Diameter (ID): 1.00" (25mm)
• Outside Diameter (OD): 1.39" (35mm)
• Overall Length: 25 feet (Box)
• Wall Thickness: .170" / .220"
• Weight LB/FT: 0.391
• Actual Burst Pressure - PSI: 300
• SAE J20 R3 Class A - PSI: 300
• 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