Flat Finishing Box

12" MEGA Drywall Flat Box

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MSRP: $389.99
Was: $389.99
Now: $350.99
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  • Expertly dispense an even, consistent layer of drywall joint compound to taped flat and butt joints on walls and ceilings.
  • A flexible brass blade allows you to provide the proper compound application and crown - whether you're applying the first fill coat or the final finish coat. Butt and flat joint edges are also feathered to perfection.
  • 10 pressure settings so you can dial in the perfect result. A deeper set pressure lid allows for easier push operation than other flat boxes on the market.
  • The lid has a fixed hinge for smoother operation and it opens extra wide for fast, easy cleaning.
  • A deeper back spine makes hand operation easier, faster and more accurate. Hard coat anodized aluminum housing for durability. Fits all major brand drywall flat box handles.
  • Hold up to 25% more mud to help speed up your drywall finishing workflow.
  • SKU: 4-769
  • UPC: 815966020258

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A flat box is used in conjunction with a flat box handle to efficiently apply a crowned, feathered coat of joint compound over taped flat seams on walls and ceilings.

LEVEL5 flat boxes feature a premium-grade aluminum housing that has been anodized for extreme durability and easy cleaning. They are fitted with a flexible brass blade holder and a stainless steel blade, as well as stainless steel skids and shoes. A crown adjustment dial provides six settings (including “wide open”), so the ideal amount of compound can be dispensed on the wall to ensure consistent, professional results.

LEVEL5 flat boxes have a premium composite pressure plate seal and beveled edges on the box housing ensure easy open and close. The pressure plate itself also opens extra wide for easy cleaning.

LEVEL5 flat boxes are outfitted with non-marring wheels with durable bearings for ultra-smooth operation.


The MEGA capacity flat boxes can hold approximately 30% more compound than standard capacity flat boxes, enabling few trips back and forth to the pump. The trade off is that MEGA capacity fla boxes are bulkier and heavier when full due to their increased height. Ultimately, the choice between the two styles is a matter of personal preference.

level5 flat box finishing a corner
level5 flat box being filled


  • Both the standard and MEGA capacity flat boxes feature higher compound capacities than previous generation.
  • All structural components are higher-gauge, aircraft-grade aluminum for durability, even under heavy commercial use.
  • New precision-machined billet aluminum body and side plates with bevelled edges.
  • Side plates are now black hard-coat anodized, significantly reducing the friction against the sweep gasket and lowering required push force.
  • New proprietary urethane sweep gasket provides less resistance, smoother operation and a better seal.
  • New hinged pressure plate provides a consistent push radius at all compound capacity levels.
  • Hinge opens wide for easy cleaning.
  • New high-durometer urethane rubber tires for more longevity.


  • Consistency of Compound - There are no strict guidelines for the consistency of the compound when using flat boxes, as it is a matter of personal preference. It is crucial to ensure that the compound is thick enough to avoid dripping down the walls or overflowing from the dispensing slot, but thin enough to be applied without excessive force. Some finishers prefer to use different consistencies depending on the surface they are working on (walls or ceilings).
  • Filling the Flat Box - The ideal way to fill the flat box is through the dispensing slot with a compound pump (#4-771) and a filler valve equipped with a flat box filler nozzle (both are included with the pump). It is also possible to manually fill the box by opening the hinged pressure plate.
  • Flat Box Handles - Flat box handles have a pinch break feature which enables you to lock the box at a specific angle and maintain it flat against the wall. To activate this mechanism, squeeze the trigger located at the end of the handle. PRO TIP: to prevent injury, keep light pressure on the pinch brake trigger when the flat box is not in use to avoid swinging and accidental contact with your knuckles or fingers.
  • First Coat - The first coat should be a "fill" coat, using the lowest crown setting of your choice (out of the 6 crown options). The purpose of this coat is to completely cover the tape and conceal the tape bevels. If you come across any air pockets or other imperfections, simply apply one or more passes over the seam until you are satisfied with the result.
  • Second Coat - After the first coat has dried, a second, thin layer can be applied using a slightly wider flat box to fill any imperfections and feather out the compound to hide the seam.
  • Final Result - When performed correctly, only two coats should be necessary, with minimal sanding required afterwards to achieve a professional finish.


7-Year Warranty

100% Satisfaction Guaranteed

LEVEL5 makes workhorse drywall finishing tools that set the standard for quality & reliability.

We back all of our tools with the strongest warranties in the industry and work hard to provide our family of finishers with the best customer service possible.

Do you have questions about your LEVEL5 Tool(s)? Call our toll-free support line at 866.562.4229 (local: 913.631.0804) or send us an email at support@level5tools.com. Our support team is available Monday through Friday, 7:30am to 4pm Central Time.

Manufacturer's  Warranty

For its full line of automatic drywall finishing tools and accessories, LEVEL5 Tools, LLC. ("LEVEL5") offers a full seven (7) year warranty to the original owner that these products will be free from defects in material and function. This warranty is valid only in the USA, Canada, Australia, the United Kingdom and Europe. A one (1) year warranty applies in all other countries/markets.

Terms & Conditions

  • The Warranty applies to the original owner and is not transferable.
  • The Warranty is limited to repair or replacement of the product, and does not cover direct, indirect, consequential, incidental or any other type of damage resulting from its use.
  • The Warranty does not cover normal wear, misuse, negligence, fire, theft, loss or intentional damage.
  • All shipments to the LEVEL5 facility must be freight paid. LEVEL5 reserves the right to determine whether to repair or replace any product covered under the Warranty. Discontinued products may be replaced with newer models when necessary.
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(3 reviews)
  • Quick and Easy

    @krugerconstruction, 21st Feb 2020


    Flat Boxes making it quick and easy. I get asked all the time if they are hard to use and worth it. I’d say they are if you do a good share of drywall, there’s so many videos on how to use them out there, the most important thing is practice it may take a few jobs to get used to them.

  • Love it

    @seamlessdrywalling, 22nd Dec 2019


    Love it when I get a chance to use my Level 5 flat boxes, here is one of the first times I ever got to run a box, still havnt used them to many times just because I do a lot of blending new into existing.

  • Quick and Easy

    Dustin Smart, 30th Aug 2018


    Works great and saved lots of time