Fill Caps

Many combinations. Amazing finishes. Lightweight Design.

Safe. Secure. Sexy.

Turn heads while working on your race car with Pro-werks' signature Easy Turn Fill Caps. Once you've added one of these amazing assemblies, you'll want to install one at every location possible on your hot rod. And you may find yourself checking things more often, just to get your hands on the Easy Turn cap again!

These lightweight, non-vented Pro-werks Fill Caps feature deep finger notches for a positive and comfortable grip, that won't hurt your hand. This design is another Pro-werks innovation, appreciated by everyone who uses them.

Precision matters.

We start with American melt 6061-T6 billet aluminum; it is precision CNC machined to exacting standards for proper fit and to create the foundation for obtaining amazing finishes.

This design uses a radial squeeze action on a Buna O-ring for a secure seal. Precision machined quick-start coarse threads make using these caps a breeze.

The large selection of Pro-Werks mounting bungs are crafted from steel, aluminum or stainless steel and available in both weld-in and bolt-on styles.

Great caps. Great colors.

The proprietary color finishing processes are available in your choice of either brilliance anodized black, red and blue or micro-polished aluminumresulting in unmatched jewelry quality finishes.

The right size matters.

Easy Turn Fill Caps come in many sizes and are packaged as complete assemblies with your choice of one of the many versatile mounting options, or each component is also available separately.

Popular uses for Easy Turn Fill Caps include:

  • Custom-fabricated tanks
  • Fuel cells
  • Rear End housings
  • Valve covers
  • Overflow tanks
  • Ice boxes for intercoolers
  • Ballast tanks
  • Inspection viewing ports

Be sure to check out the entire line up - Billet aluminum Easy Turn Fill Caps are a Pro-Werks specialty. Watch the Video below to learn more !

Proudly made here in the USA.

Note: Welding should always be performed by a qualified welder.

Customer Comments:

"I use your bolt on caps and bungs on my carbon fiber Cummins common rail valve covers. Love the quality. Thank you."
             Randy Davis, Owner of OldSkoolFab, Inc.

"I upgraded my fuel cell to an Easy Turn fill cap assembly. It wasn't long until all my friends did the same. Great product!"
             As shared with us at the
PRI Show

Finish Your Tank

We also offer a full line of weld-in plumbing bungs to complete your tank project.

Click the images below to view all the options.