Extension Cord Rating Designations

Indented on each Milspec cord is a letter designation that

defines the type and approved use of the cord. 

SJTW (UL) Water Resistant or c(UL) SJTW FT2
STW (UL) Water Resistant or c(UL) STW FT2

SJEOW (UL) Water Resistant or c(UL) SJEOW FT2
SEOW (UL) Water Resistant or c(UL) SEOW FT2

SJ (UL) Water Resistant or c(UL) SJ FT2
SJO (UL) Water Resistant or c(UL) SJO FT2
SJOW (UL) Water Resistant or c(UL) SJOW FT2
SO (UL) Water Resistant or c(UL) SO FT2
SOO (UL) Water Resistant or c(UL) SOO FT2
SOOW (UL) Water Resistant or c(UL)


S - The "S": Hard Service flexible cord for general use.
P - Parallel construction, usually uninsulated and used in products such as household extension cords, air conditioner cords and low voltage landscape cable.
J - The "J": jacket of the cord as standard 300 volt insulation.  The absence of the "J" defines the cord jacket as an extra hard service 600 volt insulation type defined by Milspec as our "Double Jacket" cord because the outer cord jacket is roughly twice the thickness of the "J" jacket that is normally used in outdoor extension cords.
V - Vacuum wire, softer and more flexible than standard SJT, usually found on retractable cord reels and vacuum cleaner power supply and extension cords because it holds up to constant winding and unwinding but still maintains its shape.
T or E - Insulation and jacket material. "T": PVC (vinyl) thermoplastic.  "E": TPE-thermoplastic elastomer rubber.
O - Oil Resistant. This was especially designed because most rubber type cords would break down and lose insulating performance when exposed to oil or grease.
W - Rated for Outdoor use. Different insulation and jacket must meet the following use temperature ranges. UL temperature range of the "T" PVC vinyl material: -31F to +140F (-35C to +60C). Milspec has formulated the PVC vinyl compound in our products to exceed this nominal range by approximately 5F. UL sets a use temperature range of the "E" TPE-rubber material at -58F too +221F (-50C to +105C). Milspec has also exceeded this range by approximately 12F.
(UL) - Underwriters Laboratories listed. UL allows the use of the logo in parenthesis rather than a complete circle on round product, like a cord.
Water Resistant - Most of Milspec's outdoor cords are now made with water resistant material. Standard vinyl and TPE- rubber cords have a tendency to absorb water if left laying in a puddle on the job site. When water comes in contact with the copper wire it starts to corrode. If the water remains in the cord it could build up until a shock path is created. When water gets in a cord it's life is shortened.
CSA - Canadian Standards Association requirements. The CSA logo is usually not abbreviated.
c(UL) & c CSA us - Since the NAFTA agreement with Canada, UL and the Canadian Standards Association, CSA, have worked together to allow CSA to list products for the USA and for UL to list products for use in Canada. The c(UL) designation says the product was tested and certified by UL to Canadian Standards and the c CSA us mark signifies that CSA tested the product and certifies it to UL Standards.
FT2 - Flame retardant. If a standard vinyl or TPE-rubber cord catches on fire, the flame can quickly burn the entire length of the cord. The Milspec jacket insulation material will prevent the spread of combustion along the cord. The cord will extinguish the flame within 30 seconds of the heat source being removed.
CL2 - Or "class 2" is a UL rating for wire that can be used for in-wall construction. Usually applies to communication cable or speaker wire.
SRDT - Is heavy duty wire made specifically for use with higher amperage equipment such as ranges, dryers and mobile home power hook-up cords. Not very flexible.
HPN - Is high-heat parallel neoprene wire made specifically for use with clothes irons, portable heaters and other such applications where high temperatures of the appliance could affect the power cord's performance.