This pencil-like coupon is screwed into an insulator which is then screwed into an NPT Bull plug Coupon Holder(code:HBP). The rod coupon standard size is Ø1/4” x 4" (Ø 6.3mm x 101.6mm), with a milled flat area for the serial number. One end is threaded for screwing the coupon into the insulator, the other is notched to accept a flathead screwdriver. The exposed surface area is 3.27 in² (2,109mm²).

Sewon standard coupons come furnished complete with insulation made from MC nylon, which has a temperature rating of 220°F (120°C). Insulation for higher temperature requirements is available and should be specified when required. The higher temperature insulation materials are:

Teflon - 500°F (260°C)

Rulon - 550°F (288°C)

Ceramic - 1472°F (800°C)