Flap Fittings & Gas Struts: Replacement Parts Suitable for Wall Units

March 3, 2026

A gas strut assists with opening and holding furniture flaps open using compressed gas within a cylinder, with its force measured in Newtons.

When cabinet fronts on existing furniture no longer stay open on their own or drop downwards when opened, worn lift fittings are usually to blame. Especially with wall-mounted kitchen cupboards or modern wall units featuring handleless fronts, these components are subject to continuous strain. Heavy solid wood wall unit fronts also place high demands on the mechanism over the years. This guide is aimed at fitters and experienced tradespeople who want to properly identify, calculate, and replace defective flap mechanisms with compatible replacement parts.

Key Buying Criteria for Gas Struts and Flap Stays

Replacing a lift fitting requires precision. A visually identical component is useless if the technical specifications differ. The following parameters must be checked thoroughly.

Force in Newtons (N)

The lifting force is the most important factor and is specified in Newtons (N). This value is usually printed on the cylinder of the old strut, for example as "100N" or "0150N". The range for standard furniture typically extends from 50 N to 250 N. Selecting the strut force works much like balancing a tyre – if it is too weak, the flap drops down; if it is too strong, it can hardly be closed and the hinges risk being torn from the carcass. The required force depends on the flap weight (including the handle) and the flap height.

Length and Installation Dimensions (mm)

The second critical measurement is the length. Gas struts are always measured in their fully extended state. The relevant measurement is the distance from hole centre to hole centre of the ball joints at each end. Common lengths in furniture construction range between 245 mm and 270 mm. Furthermore, the stroke (the travel distance of the extendable piston rod) is crucial. An incorrect stroke changes the opening angle of the flap, which is typically 75°, 90°, or 110°.

Fixing Type and System 32

The mounting plates at the ends of the strut must match the carcass and the front panel. In industrial furniture manufacturing, System 32 is used, where the drill holes have a 32 mm spacing. Different brackets are required for fixing to wood-based materials or aluminium frames. When mounting into wood, matching countersunk wood screws and furniture screws are used (usually 3.5 mm or 4 mm diameter, PZ2 drive).

Overview of Types and Options

Depending on the construction of the cabinet, different fitting types are used, varying in their mechanics and load capacities.

Standard Gas Struts

These are traditional cylindrical dampers consisting of a pressure tube and a piston rod. They are cost-effective, easy to replace, and suitable for single-piece upward-opening flaps made of chipboard or MDF. They often feature end-position damping to prevent a hard stop at the maximum opening angle.

Heavy-Duty Flap Fittings

For very large or thick fronts, a simple strut is often insufficient. Here, gas struts for heavy flaps are used. These systems frequently utilise more sophisticated kinematics and stronger cylinders to lift weights from 5 kg to over 15 kg safely and hold them in any position (multi-position stop).

Mechanical Flap Stays

In contrast to gas-filled cylinders, mechanical flap stays operate using friction. The resistance in the joint is adjusted to the weight of the front via an adjusting screw. They contain no gas that could escape, but they do not provide the automatic lifting support of a gas strut. The user must guide the flap manually to the desired position, where it then stays.

Which Fitting for Which Situation? (Decision Guide)

To ensure compatibility and preserve the lifespan of the furniture, the replacement part must match the physical characteristics of the front panel precisely. Use flap fittings designed for the respective material and weight.

If the flap is small and lightweight (e.g. 300 mm high, chipboard): Choose a strut rated from 50 N to 80 N.
If it is a standard wall unit (e.g. 400 mm high, MDF): Models from 100 N to 150 N are usually the right choice.
If the front is made of solid wood or is very large: Opt for struts from 200 N to 250 N, or upgrade to heavy-duty fittings.
If the flap opens downwards (drinks cabinet): You do not need a gas strut here, but rather a dedicated stay for downward-opening fronts (drop-down lid stay) that brakes the descent.

Installation Guide: How to Replace Gas Struts Correctly

For most systems, replacement can be carried out without tools at the joint itself; tools are only required for the mounting plates.

Required Tools:

Screwdriver (Pozi PZ2)
Small flat-head screwdriver
Tape measure (in mm)

Step-by-Step Instructions:

Removal: Open the flap and support it securely (enlist a second person to help). Place the small flat-head screwdriver under the metal spring clip on the ball joint of the old strut and prise it up slightly. Pull the strut off the ball stud.
Inspection: Check the printed Newton rating on the old cylinder. Also check whether the ball studs on the carcass brackets are worn.
Replacing brackets (if necessary): Loosen the old screws. If the new brackets have a different hole pattern, use furniture connectors or wooden dowels to plug the old holes before drilling new ones.
Fitting: Simply push the ends of the new gas strut onto the ball studs until the metal clip audibly clicks into place. Pay attention to the orientation: with most manufacturers, the thick cylinder must point upwards (towards the carcass top) and the thin piston rod downwards (towards the front) to ensure the internal oil lubrication and end-position damping function correctly.

Frequently Asked Questions (FAQ)

How do I calculate the required force in Newtons?

The force depends on the weight of the flap including attachments such as a furniture handle. A common rule of thumb for standard hinges is: flap weight in kg × 10 = required force in N. For a 3 kg flap, you would therefore require approximately 30 N. Because struts are usually used in pairs and leverage principles apply, two struts of 60 N each are often selected in practice for this weight. Primarily, refer to the value on the original strut.

Can I install a stronger gas strut than before?

No, this is not recommended. If you install a 200 N strut instead of a 100 N strut, the flap can only be closed with substantial effort. The constant counter-pressure will cause the concealed hinges to tear out of the chipboard or distort the front.

How do I measure the length of a gas strut correctly?

Measurements are taken when fully extended. Apply the tape measure and measure precisely from the centre of one ball joint to the centre of the other ball joint. The overall length is less relevant than this centre-to-centre distance.

What does N stand for on the gas strut?

The N stands for Newton, the physical unit of force. It indicates how much pushing force the cylinder exerts to push the furniture flap upwards and hold it open.

Why does my flap slam shut?

Gas struts are primarily lifting aids, not closing dampers. If the front slams shut hard, the cabinet lacks separate door dampers (soft-close elements), which are usually integrated into the hinge cup or retrofitted as clip-on dampers.