C73-705 | 2-3/4 in. BLACK FILL CAP WITH SILVER ALUMINUM 6 BOLT FUEL CELL BUNG2-3/4 in. BLACK FILL CAP WITH SILVER ALUMINUM 6 BOLT FUEL CELL BUNGSide of AssemblyBottom of BungBlack CapShown with optional Lanyard Chain Kit installed.Installed on a Black Fuel Cell.Detail of bungProudly Made in the USA.A satisfied customer shared their installation.Installed on an Aluminum Tank.



Price: $94.99

Buy Now

2-1/4-10 Straight Thread
6 on 4.438 in. Dia. Bolt Circle
3/4 in. Bung Height

Includes mounting hardware and Buna gasket

Made in the USA

(Cap Replacement O-Ring is C73-788-A)


Pro-Werks provides another new improvement for racers and rodders; fuel cell users can now easily upgrade from the original manufacturer provided, 6 or 12 bolt flanged, less than desirable, troublesome flip-latch style filler or bail cap - to the popular easy turn Fill Cap Assembly from Pro-Werks.

Say good-bye to pry bars.


This assembly is a simple bolt-on installation as a replacement, or right at home in new custom tank fabrication, and includes the necessary stainless mounting hardware with the Buna flange gasket.

The positive grip finger notches of the non-vented Easy Turn Caps are easy to get a hold of, and won't hurt your hand. This design is another Pro-Werks innovation, appreciated by everyone who uses them. The cap also has quick acting coarse threads with a starter nose to accurately lead the cap into position - a very nice feature when you are taking care of business in the dark. Each is standard with a special positive sealing "radial squeeze" Buna O-ring, which also holds the cap secure.

Great caps. Great colors.

Easy Turn caps are available in a large selection of Pro-Werks Brilliance Anodize Finish colors or beautiful Micro-polished aluminum. The bung of this assembly is also available in your choice of two anodized colors, Silver or Brilliance Black. The extensive selection of color combinations gives you the opportunity to match your individual style.

Keep your cap close.


The signature Pro-Werks Fuel Cell cap also includes a built-in lanyard boss, enabling the use of the optional lanyard chain to conveniently keep the cap close by - if you so desire.

Both the cap and bung are precision CNC machined light weight billet aluminum, right here in the USA.

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 !

You can always count on Pro-Werks to do it right.

Customer Comments:

"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.



How much do I need to tighten a fill cap?


It is not necessary to bottom the fill cap into the bung−just  
adequately seat the O-ring. The radial squeeze action on the O-ring creates a positive seal and helps prevent the cap from coming loose.



What should I use to lubricate the Buna O-ring?


Applied periodically, a light coating of Dielectric grease has proven to work well as an O-ring lubricant.



Is Buna rubber compatible with my fluid?


Buna is a synthetic rubber compound suitable for use with most fluids. Buna components may need to be replaced by a material compatible with the specific chemistry of some fluids.


2-3/4 in. Black Fill Cap: C73-780-LB
Outside Grip Diameter: 3.200 in.
Height: 0.312 in.
Thread: 2-1/4-10
Height: 0.750 in.
Inside Grip Diameter: 2.750 in.
Aluminum Fuel Cell Bung: C73-712
Diameter: 2.625 in.
Thickness: 0.25 in.
Thread: 2-1/4-10
Thickness : 0.50 in.
Holes: 0.265 in.
Dia. Hole
Bolt Circle: 6 on 4.4 in. Bolt Circle
Outside Diameter: 5.25 in
; ; ; ;