Roller Runners vs. Ball-Bearing Full Extension Runners: Installation Dimensions Explained

February 1, 2026

A ball-bearing full extension runner extends to 100 per cent and typically requires exactly 12.7 mm of side clearance, whereas a traditional roller runner is often designed as a single extension operating with 12.5 mm clearance and bottom-mounted installation.

When building carcasses or repairing existing drawers, joiners and fitters frequently face the challenge of choosing the correct runner system. The decision between a roller runner and a ball-bearing runner affects not only running smoothness and load capacity, but also dictates the exact cutting dimensions of the drawer components. Choosing the right runner is like laying the foundations of a house – if the dimensions are off by even a millimetre, the whole assembly will jam or the drawer will rub against the cabinet side. This guide details the technical differences, installation dimensions, and weight ratings to help you choose precisely the right fitting for your furniture project.

Key Purchasing Criteria: Installation Dimensions and Tolerances

The fundamental distinction between these systems lies in their kinematics and carcass space requirements. When replacing existing runners or planning a new cabinet, you must calculate the following parameters precisely.

Side Clearance and Drawer Width

The installation clearance describes the gap between the inside of the carcass and the outer edge of the drawer side.

Ball-bearing runner: These runners generally require exactly 12.7 mm (equivalent to half an inch) of space per side. The drawer box width is therefore calculated as the internal carcass width minus 25.4 mm.
Roller runner: These standardly require 12.5 mm clearance per side. The drawer must therefore be 25.0 mm narrower than the internal width of the cabinet.

If this minute difference of 0.2 mm per side is ignored, a ball-bearing runner can end up under tension, potentially forcing the steel ball bearings out of their cage or making the movement extremely stiff.

Nominal Length and Carcass Depth

The nominal length defines the length of the runner when closed. It must match the internal carcass depth, usually factoring in 3 mm to 5 mm of clearance to the rear panel. Lengths are structured in modular increments, typically ranging from 250 mm - 800 mm. For compact bathroom units or office pedestals, drawer runners 300 mm are frequently used. For standard kitchen base units, lengths like 500 mm or 550 mm are most common.

Load Capacity and Leverage

The maximum load capacity is specified in kilograms and always applies to the pair (two runners) under an evenly distributed load.

A standard roller runner generally carries 20 kg to 25 kg. It quickly reaches its limits when loaded with wide stacks of pans or heavy tools.
Ball-bearing runners offer significantly higher reserves due to their telescopic construction made from hardened steel. Standard versions carry 35 kg to 45 kg.
For workshop trollies or deep larder units, heavy-duty drawer runners exist that reliably support loads from 80 kg to over 130 kg, even at extensive lengths such as 900 mm or 1200 mm.

Extension Type: Full Extension vs. Single Extension

A full extension allows the drawer to be pulled out to 100 per cent of its depth from the carcass. The user enjoys unrestricted access to all contents right up to the back panel. A single extension (partial extension), by contrast, stops short by design – usually leaving around 25 per cent of the drawer concealed inside the cabinet. While sufficient for simple clothing drawers, this is impractical for deep kitchen cabinets.

Types and Options Overview

The Traditional Roller Runner

The roller runner drawer runner consists of two epoxy-coated steel profiles per side. One profile screws to the carcass wall, while the other fits beneath the bottom of the drawer. Movement is facilitated by plastic rollers (usually POM or nylon).

Advantage: Very forgiving of installation errors, resistant to dust, and the drawer can be removed entirely simply by lifting it over the front roller.
Disadvantage: Typically only available as a single extension, lower load capacity, and lateral play that can make the movement feel slightly loose.

The Ball-Bearing Full Extension Runner

Here, interlocking steel profiles glide on tiny steel ball bearings held inside bearing cages. This telescopic design enables complete extension. Whenever full access to storage space is needed, full extension drawer runners are the primary choice.

Advantage: Exceptionally smooth operation, high lateral stability (no wobbling), and high load ratings.
Disadvantage: Zero tolerance regarding side clearance. If the drawer box is made too wide, the system will bind immediately.

Specialist Machining: 17 mm Groove

A specific variant of the ball-bearing runner is designed for groove mounting. In this case, a continuous groove exactly 17 mm wide is routed into the drawer side (usually solid wood). The runner sits flush inside this groove. This reduces the required side clearance to a minimum and is frequently used in traditional furniture or shallow keyboard pull-outs.

Comfort Mechanisms: Soft-Close, Self-Closing, and Push-to-Open

Modern runner systems are enhanced with mechanical components to improve user convenience. It is essential to distinguish between these mechanisms correctly:

Soft-close: A combination of a spring and a hydraulic or pneumatic damper. When the drawer is pushed shut, the damper absorbs the kinetic energy and gently pulls the drawer closed over the final centimetres in complete silence. Drawer runners with soft close are the standard in modern kitchen manufacturing.
Self-closing: A purely mechanical spring mechanism without damping. The drawer is actively pulled shut over the last few centimetres, closing with an audible click against the carcass. Often found in entry-level self-closing drawer runners. (In roller runners, a natural self-closing effect is often created by a sloping profile over the final few centimetres).
Push-to-open: A release mechanism for handleless fronts. A light press on the drawer front releases a tensioned spring that pushes the drawer open. Note: Push to open drawer runners and soft-close are mechanically mutually exclusive in their basic form, as they rely on opposing forces. (Combined systems do exist, but they are mechanically intricate and require specialist synchronisation rods).

Which System for Which Application? (Decision Guide)

Choosing the correct runner depends heavily on the application and the type of furniture.

For wide kitchen cabinets: A kitchen cabinet pull out 60 cm demands a ball-bearing full extension runner. The weight of plates or pans requires a high load capacity (at least 35 kg), and the full extension ensures that even items at the very back can be reached without bending down.
For workshops and campervan conversions: Telescopic runners are essential here. A heavy tool chest or a rear slide-out in a van requires lengths from 800 mm to 1200 mm and load capacities beyond 80 kg.
For simple office pedestals or children's bedroom furniture: When budget is the primary factor and the weight of pens and paper is light, a roller runner is entirely sufficient. The quick lift-out removal mechanism is also practical for easy cleaning.

Installation Guidelines for Fitters

Professional fitting requires precision. For mounting inside the carcass, the System 32 pattern is used – a standardised line of holes spaced at 32 mm intervals with a 5 mm hole diameter.

Marking and positioning: The height of the runners inside the carcass must be strictly parallel. With ball-bearing runners, the rail is typically mounted centrally along the height of the drawer side. With roller runners, the L-shaped profile is screwed underneath the drawer base, defining the bottom edge of the drawer box.
Fixing: Use chipboard screws (often called Euro screws) with countersunk or pan heads, depending on the hole design of the runner. A diameter of 3.5 mm or 4 mm with a PZ (Pozidriv) or TX (Torx) drive provides optimal grip in chipboard or MDF.
Checking tolerances: Ball-bearing runners often feature small tabs on the carcass rail that can be bent slightly to compensate for inaccuracies of up to 0.5 mm. Nevertheless, always check the side clearance with vernier callipers before tightening the screws completely.

Frequently Asked Questions (FAQ)

Can I replace a roller runner with a ball-bearing full extension runner? Yes, this is generally possible, but it requires great precision. Because roller runners require 12.5 mm clearance and ball-bearing runners require 12.7 mm, the existing drawer box might be marginally too wide. Furthermore, the mounting position on the drawer side (base-mounted vs. side-centred) must be recalculated and re-drilled.

What does the '17 mm groove' specification mean for runners? This refers to a specific design of ball-bearing runners. Instead of being surface-mounted onto the outer face of the drawer box, a 17 mm wide groove is routed into the wooden drawer side. The runner is recessed into this groove, saving space and creating a neater appearance.

What is the difference between soft-close and push-to-open? Soft-close (damping) slows down a vigorously closed drawer and pulls it silently shut over the last few centimetres. Push-to-open (tip-on) is designed for handleless fronts: pressing the closed front releases a spring that pops the drawer open. The two mechanisms work in opposite directions.

What nominal length do I need for my drawer? Measure the internal depth of your cabinet carcass (the inside dimension from the front edge to the rear panel). Deduct at least 3 mm to 5 mm from this measurement. Then select the nearest smaller available nominal runner length. For instance, with an internal carcass depth of 510 mm, choose a runner with a 500 mm nominal length.

How do you disconnect a ball-bearing full extension runner to remove the drawer? Pull the drawer out completely. Inside the telescopic profile on both runners (left and right), you will find a small plastic release lever. Press the lever up on one side and down on the other (or both in the same direction, depending on the manufacturer). Keep the levers held while pulling the drawer straight forwards out of the runner tracks.