5/16″ diameter bulb


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5/16″ diameter bulb is used for older windows that are warped or no longer seated properly.

Professional Contractor grade. OEM+ quality. Produced in extruded TPE (Thermoplastic Elastomer) offering the flexibility of a thermoplastic along with the functional performance of conventional thermoset rubber. Use to replace worn out kerf window seals with ease. Available in 4 colors (White, Tan, Brown, and Black) and sold in 4 different lengths for any job. Simply cut to desired length.

The perfect OEM replacement. Helps prevent water damage. Offers better insulation helping to reduce heating & A/C costs. Lowers outside noise and wind howling.


  • Manufactured from OEM+ quality Thermoplastic Elastomer (TPE)
  • Most common bulb size – 1/4″. Also available in 5/16″ bulb diameter.
  • 3/16” Kerf depth with standard 1/32” Kerf width.
  • Slip Coat on top of bulb decreases operating force in both sliding and sweeping applications
  • 4 Lengths to choose from – 25’, 50’, 100’, 500′
  • 4 Colors to match most requirements– White, Tan, Brown, and Black
  • Made in the USA.


  • KerfSeal Offers the perfect OEM replacement seal for wood frame, casement windows and doors that take seal-in kerf weatherstrip.
  • Extremely flexible TPE Elastomer that withstands high heat and extreme cold (up to 60 degrees below zero).
  • Offers you better insulation keeping out the elements including water, wind and insects.
  • Easy insulation – Simply cut to length and push into kerf cut channel.

Our warehouse stocks over 25,000 feet of this one item at any given time to insure super-fast shipping of your order.

ALL orders ship within (1) business day.


White, Tan, Dark Brown, Black


100', 25', 50', 500'