The Ultimate Dropper Post Buying Guide

What is a dropper post?

A dropper post is an adjustable seatpost that moves up and down at the press of a lever. You pedal efficiently with the saddle raised, then drop it instantly when you hit steep, technical, or loose terrain. It’s one of the biggest confidence and control upgrades you can make to a mountain bike – and increasingly, to gravel and adventure bikes too.

Why use a dropper post?

More control

Lowering the saddle drops your centre of gravity and gives you more room to move confidently over rough terrain.

More confidence

With the saddle out of the way, steep descents, roots, rocks and tight corners feel much more manageable.

More speed and flow

The ability to quickly change saddle height helps you stay low and active, carrying momentum through corners and features.

More efficient climbing

Raise the saddle for a powerful pedalling position, then drop it again the moment you need extra clearance.

Key things to consider

When choosing a dropper, there are a few important things to get right:

• Seatpost diameter
• Travel (how much the post moves)
• Your saddle height (for fitment)
• Your frame’s maximum insertion depth
• Dropper minimum insertion
• Internal or external cable routing

Seatpost diameter

Your seatpost diameter must match your frame exactly. This is fixed by the frame.

Common sizes

• 27.2 mm – common on gravel bikes and some older XC bikes
• 30.9 / 31.6 / 34.9 mm – the main diameters used on most modern mountain bikes. Between them, these three sizes cover the vast majority of current MTB frames.

How to find your diameter

1. Remove your existing seatpost.
2. Look for the size stamped or etched into the post.
3. If it’s not visible, check your frame’s specifications.

You’ll need this before using the Sizing Tool.

How to measure your bike for a dropper

1) Saddle height for dropper fitment

For droppers, we’re interested in how much post needs to sit above the frame. Measure from the top of your frame’s seat clamp → to the saddle rails when the saddle is at your normal pedalling height.

2) Maximum insertion depth

Remove your current post and measure how far it slides into the frame before it stops. This may be limited by bottle bosses, bends, pivots or internal frame features.

3) Seatpost diameter

As above – take this from your existing post or your frame spec.

Minimum insertion

Every dropper has a minimum insertion requirement – the minimum amount of post that must remain inside your frame for safe use.

You’ll find minimum insertion values:

• In each dropper’s dimension chart on its product page
• And in the full dimension table on our data page

The Sizing Tool checks minimum insertion automatically and hides anything unsafe for your frame.

Using the Ascend Components Sizing Tool

The tool needs just three inputs:

1. Seatpost diameter
2. Saddle height (seat clamp → saddle rails)
3. Your frame’s maximum insertion depth

It then shows you all Ascend Components droppers that will:

• Fit your diameter
• Reach your saddle height
• Fit inside your frame’s insertion depth
• Meet minimum insertion requirements

Try it here: Ascend Components Dropper Seatpost Sizing Tool.

Travel length – how much do you need?

Travel choice depends mainly on your height and your riding style.

Rider height

Taller riders often benefit from longer travel, as they have more room above the frame. Shorter riders typically choose shorter or mid-length travel.

Riding style

Aggressive trail & enduro: Longer travel for maximum clearance.

XC & downcountry: Moderate travel for a balance of weight and clearance.

Gravel: Typically 70–125 mm for control on steep or loose descents.

The common mistake

“I’m tall, so I’ll just get the longest drop.”

Longer droppers need much deeper insertion inside the frame. Many riders can’t fit a 180–200 mm post because their frame doesn’t have the internal depth, even if their height would suit it.

The correct approach

Choose the longest travel that suits your riding and physically fits inside your frame.

The sizing tool checks this automatically using your measurements.

Routing types

Internal (stealth): Cable runs inside the frame – standard on most modern MTBs.

External: Ideal for bikes without internal cable ports, or for riders who prefer the simplicity of external routing and don’t want the extra hassle of fitting an internally routed post.

Dropper spec highlights

Here’s a quick comparison of the main Ascend Components dropper families. For full dimension data (lengths, insertions, stack heights and weights) please see: Ascend Components Dropper Seatpost Dimension Data – All Models .

Which Ascend Components dropper should you choose?

Ascend Components Flight

Quite possibly the best value dropper post on the market. Flight is our dependable workhorse – smooth, reliable and brilliantly priced. A true all-rounder suitable for everything from XC to enduro.

Ascend Components Flight SL

Our top-of-the-range post. Lighter, with a shorter insertion depth than Flight, making it easier to fit across more frames. Designed for riders who want a premium, lightweight option for anything from XC to enduro.

Ascend Components Adapt

Our most flexible post. Adapt features travel adjust in 5 mm increments, letting riders fine-tune the perfect drop. Ideal for frames with tight insertion limits or anyone who wants to customise their setup precisely.

Ascend Components Flight SL Gravel

A lightweight 27.2 mm dropper built specifically for gravel and adventure bikes. Designed to give you extra control and confidence on loose, steep and technical terrain without adding unnecessary weight.

Ascend Components Flight External

Our external-routed MTB dropper, for bikes without internal cable routing or riders who simply prefer the ease of external cabling. Same great performance as Flight, with simple, reliable external actuation.

Ascend Components Flight External Gravel

A 27.2 mm externally routed gravel dropper for frames without internal ports, or riders who don’t want the hassle of internal routing. Lightweight, smooth and ideal for bikepacking, gravel and mixed-terrain riding.

Ascend Components Flight Kids

A shorter, lighter, easier-to-actuate dropper designed specifically for younger riders. Gives kids the same confidence-boosting control adults enjoy, in a package that fits smaller frames and smaller hands.

Final thoughts

Once you know your measurements, choosing the right dropper is straightforward. Our sizing tool will guide you through what fits, and the full dimension table is there if you want to dig into every last millimetre.

And if you ever need help, we're always happy to point you in the right direction.