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Techflex® Spark Plug Boot Insulators

Fiberglass Spark Plug Ignition & Wire Protectors - Max Temp 1200ºF

Insultherm Spark Plug Boot Insulators

  • Resin Coated Fiberglass
  • Will Not Burn or Support Combustion
  • Easy, No Tool Installation
  • Operating Temps: -94°F to 1,202°F (-70°C to 650°C)
  • Extremely Abrasion and Cut Resistant
  • Resists Common Chemicals & Solvents
  • Available In 4 Colors
  • Melt Temp: 2,048°F / 1,120°C

Insultherm braided fiberglass sleeving has been the first choice among automotive professionals and enthusiasts alike for many of their thermal protection applications. These innovative sleeves offer the same high temperature protection in an easy slip on sleeve that will extend the life of expensive spark plug wires by protecting them where they need it most... at the boot. Just slip these 3/4” diameter double thickness (triple thick at the sewn end) sleeves over any spark plug cable and boot (even right angle boots) to protect them from engine temperatures up to 1,200°F. Once installed, the sleeves require no clearance from hot surfaces, and can even rest directly on hot exhaust headers without affecting performance.

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Inside Diameters Are Measured as Round Not Flat

Product Details

Insultherm Spark Plug Boot Sleeves are completely non-conductive, resist all engine chemicals, will not support combustion, and provide an easy, economical solution to the challenge of wire protection in the cramped, high temperature environment of any high performance engine compartment.

Product Specifications

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Part #
Diameter Wall Thickness Bulk Box Colors
No Ring-Easy Install
4 1/2"
7 1/2"
With Ring
7 1/2" FCU0.75 3/4" .085" 144 4

**NT in-stock color; all other available by special order only NT, BL, BK, RD 

Physical Properties
Monofilament Thickness (ASTM D-204) NA
Flammability Rating VW-1
Recommended Cutting Scissor
Colors 4
Wall Thickness .085
Tensile Strength - Yarn (ASTM D-2265) lbs. NA
Abrasion Resistance High/td>
Specific Gravity 1.0 - 1.8
Moisture Absorption % (ASTM D-570) .01


Hard Vacuum Data (ASTM E-595 at 10-5 torr)
TML .02
CVCM .01
WVR .00
Smoke D-Max (ASTM E-662) NA
Outgassing Low


Chemical Resistance 

1=No Effect   2=Little Effect   3=Affected   4=More Affected   5=Severely Affected
Aromatic Solvents 1
Alipahtic Solvents 1
Chlorinated Solvents 1
Weak Bases 1
Strong Bases 1
Salt Water (O-S-1926) 1
Hydraulic Fluid (MIL-H-5606) 1
Lubricating Oil (MIL-L-7808) 1
De-Icing Fluid (MIL-A-8243) 1
Strong Acids 2
Strong Oxidants 2
Esters/Ketones 1
UV Light 2
Petroleum 1
Fungus (ASTM G-21) 1
Salts 1


Operating Temperatures
Minimum Continuous -94°F/-70°C
Maximum Continuous (MIL-I-23053) 1,202°F/650°C
Melt (ASTM D-2117) 2,048°F/1,120°C


Other Information
Halogen Free Yes
RoHS Yes

Product Manuals

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