Front Extension as an Alternative to Blum Antaro — Compatible & Matching

A front extension is a drawer system where the furniture front is connected directly to the drawer sides and runner tracks, with compatibility to existing systems defined by standardised hole patterns in System 32 and the exact nominal length in millimetres.

In professional furniture construction and kitchen fitting, the question often arises regarding suitable components for repairs, extensions, or the complete assembly of new cabinets. When an existing drawer system needs replacing or new units are planned, an alternative to Blum Antaro is frequently sought. A runner system functions like the chassis of a car – if the mounting points and nominal lengths do not align precisely, the front cannot be fitted and the mechanism jams.

This guide is aimed at joiners and skilled fitters. It highlights the technical requirements needed to properly plan drawer systems and identify compatible replacement parts or alternatives for common branded products.

What to Look for Regarding Front Extension Compatibility

To ensure that a front extension can be fitted as a replacement for Blum or to suit other established kitchen systems, hard technical facts must be checked. Visual similarities between drawer sides play a secondary role; the crucial factor is the mechanical interface with the cabinet.

System 32 and the Hole Pattern

Virtually all modern kitchen cabinets are based on System 32. This means:

• The spacing of the drill holes in the vertical row is exactly 32 mm.
• The distance from the front vertical row of holes to the front edge of the cabinet (excluding the front panel) typically measures 37 mm.
• The diameter of the drill holes for the fixing screws (e.g. Euro screws) is 5 mm.

Runner tracks compatible with Blum or other industry standards feature fixing positions precisely aligned with this grid.

Nominal Length and Cabinet Depth

The nominal length (NL) indicates the length of the runner track and the drawer side. It determines how much internal depth the drawer requires inside the cabinet. Standard nominal lengths in kitchens range between 250 mm - 550 mm. The clear internal cabinet depth must be at least the nominal length plus a 3 mm to 5 mm installation tolerance. Anyone replacing a defective runner with a 400 mm nominal length, for example, will find matching mechanical counterparts in drawer runners 400 mm. For slightly shorter versions, such as in bathroom furniture, drawer runners 350 mm are frequently used.

Runner Type: Undermount vs Side-Mounted Installation

Modern front extensions used as an alternative to Blum Antaro almost exclusively utilise undermount runners. Here, the track sits concealed beneath the drawer base and is invisible from the outside. This fundamentally differentiates them from basic telescopic runners that are screwed to the sides of the drawer box. Anyone retrofitting such a system will definitely require undermount drawer runners to achieve the same smooth running action and visual finish.

Suitable Components for Kitchen Fitting

Depending on where they are used within the cabinet, the requirements for load capacity and functionality will change.

Full Extension for Maximum Visibility

In the kitchen, full extension is the standard for front extension drawers. It allows the drawer to be pulled out 100% from the cabinet carcass. This ensures that items stored at the very back of the drawer remain accessible without straining. A partial extension, by contrast, stops at around 75% and is more commonly used in basic desk pedestals. For kitchen projects, full extension drawer runners are essential.

Load Capacity for Pan Drawers and Larder Units

A wide front extension loaded with crockery, pots, or tinned goods requires a heavy-duty runner system. While standard drawers are usually rated for 30 kg, wide cabinets (from 80 cm) frequently require runners with a load capacity of 40 kg to 50 kg. In these cases, fitters rely on heavy-duty drawer runners to prevent the front from sagging when fully extended.

Installing Waste Bins in Front Extensions (40 cm / 45 cm)

A classic application for high front extensions is the waste separation system beneath the sink. When fitters plan a built-in waste bin for a front extension in a 40 cm or 45 cm wide cabinet, the runner must carry the combined weight of the containers and the refuse. For narrow sink units, a kitchen base cabinet pull-out 40 cm is ideal. The waste sorting systems are either screwed to the base of the drawer or hung into dedicated frames mounted between the drawer sides. Important: In sink cabinets, the installation depth of the waste trap must be taken into account, which is why shorter nominal lengths (e.g. 400 mm instead of 500 mm) are often installed here.

Installation and Retrofitting: Technical Implementation

Fitting a front extension or replacing a runner track requires precision.

Required tools:

• Cordless screwdriver with matching bits (usually PZ 2 for chipboard screws)
• Tape measure or folding rule
• Spirit level or try square
• Bradawl (for carcasses without pre-drilled System 32 holes)

Installation steps:

1. Position the runners: The cabinet tracks of the undermount runner are secured to the side panels. The front fixing screw is typically placed 37 mm from the front edge.
2. Check alignment: Both tracks must be screwed into the cabinet precisely parallel and at the exact same height. A discrepancy of just 1.5 mm will cause binding and friction.
3. Assemble the drawer: The back panel, drawer base (usually 16 mm chipboard), and drawer sides are screwed together.
4. Front attachment: The front fixing brackets are screwed to the inside of the furniture front and subsequently clipped into the drawer sides.
5. Adjustment: Using the adjustment screws on the drawer sides (usually concealed beneath a cover cap), the front can be adjusted in height, side-to-side, and tilt to achieve an even gap reveal.

FAQ – Replacement Parts and Compatibility

Can I retrofit a door damper or drawer damper as a replacement for Blum? Yes, provided the mechanical parameters match. For drawers, the soft-close damping function is usually integrated directly into the runner track. If the damper is defective, the complete runner generally needs to be replaced. Swapping it for compatible soft-close drawer runners is straightforward, provided the nominal length and hole pattern match. For hinged doors, dampers are often clipped directly onto the concealed hinge or integrated directly into the hinge arm.

What is the difference between push-to-open and soft-close damping? In their basic mechanical form, these two systems are mutually exclusive. A soft-close damper slows the drawer down as it closes and pulls it gently shut. Push-to-open (often used on handleless fronts) is a spring mechanism that pops the drawer open when pressed. Anyone planning handleless frontals will definitely require push-to-open drawer runners.

Which hinges match my kitchen cabinets? When replacing a hinge on a kitchen cabinet, measure the diameter of the cup hole in the door. The standard for a concealed hinge cup is 35 mm. You also need to know the mounting type: a full overlay is used when the door completely covers the front edge of the cabinet side panel. A half overlay is used for twin doors sharing a central dividing partition.

Are the drill holes for front extensions always identical? Attaching the runners to the cabinet carcass generally follows System 32 and is highly standardised. However, fixing the front to the drawer sides (the front fixing brackets) varies by manufacturer. If you are using a complete system (runner, drawer side, front fixings) as an alternative to Blum, you will often need to drill new holes in the front panel, as the insertion dimensions of the front fixings can vary in millimetres. The cabinet carcass drill holes, however, can usually be reused on a 1:1 basis.