Short answer: 53mm. Your portafilter is 54mm, but the tamper that goes in it is 53mm.
If you own a Breville or Sage machine and you're about to buy a tamper, this is the one thing worth getting right. It is the most common ordering mistake Breville owners make, and half the internet gives the wrong answer.
Why the two numbers are different
The 54mm figure describes the portafilter — the outside of the basket rim, and the part Breville prints on the box. The tamper doesn't sit on the rim. It goes down inside the basket, and the inside bore of a Breville basket measures about 53mm.
So a 54mm tamper won't drop in. It catches on the rim, and either you force it — which tilts the puck, which is the exact thing a tamper is supposed to prevent — or it simply sits on top and does nothing.
The sizes, per part
| Part | Size for a Breville 54mm machine | Why |
|---|---|---|
| Portafilter | 54mm | Measured at the basket rim |
| Tamper | 53mm | Goes inside the basket |
| Dosing funnel | 54mm | Sits on the rim |
| Basket | 54mm | Use the one your machine came with |
Both numbers being on the same order is correct and not a mistake. A 54mm funnel and a 53mm tamper is what a properly sized Breville setup looks like.
Which machines this applies to
Every Breville and Sage machine with a 54mm group: Bambino, Bambino Plus, Barista Express, Barista Express Impress, Barista Pro, Barista Touch and Infuser.
It does not apply to the Breville Dual Boiler, Oracle or Oracle Touch. Those take a 58mm portafilter and a 58mm tamper, and nothing from the 54mm range fits them. If that's your machine, our 58mm range is the right shelf.
What about listings that say 53.3mm or 53.5mm?
Those are the same size, described more precisely. Basket bores vary by a few tenths of a millimetre between production runs, so manufacturers pick a number somewhere in that range. Anything from 53mm to 53.5mm will seat in a Breville basket. What won't seat is a true 54mm.
Be careful with listings titled "54mm tamper for Breville" that mention 53.3mm further down the description. Those are usually 53mm tampers with a 54mm title written for search. Sometimes they're genuinely 54mm and will not fit. Read to the bottom before ordering.
Does a tighter or looser fit matter?
A little. A tamper noticeably smaller than the basket — say 51mm in a 53mm bore — leaves a ring of untamped grounds around the edge, and water will run straight down that ring instead of through the coffee. That's channeling, and it tastes sour and thin.
53mm in a Breville basket leaves the small clearance you want: enough to go in and come out cleanly, not enough to leave a gap.
What we sell
Our adjustable depth tamper comes in 53mm for exactly this reason, and it's labelled 53mm (Breville 54mm) on the product page so there's nothing to work out. The collar rests on the basket rim and stops at the depth you set, which takes the other guessing game — how hard to press — out of it too.
If you're buying more than one tool, the Breville 54mm Puck Prep Kit is the tamper, a 54mm dosing funnel, a WDT tool and a tamping mat, already in the right sizes. It's $84.99 against $111.96 bought separately, and it exists mainly so nobody has to make this 53-or-54 decision at all.
Still not sure?
Measure the inside diameter of your filter basket with a ruler — the number you get is your tamper size. Or check the size guide, or send us your machine model and we'll tell you. Gabriel answers these himself, and he'd rather answer an email than process a return.
Dialed Espresso Co. labels every product with the machines it fits — and the ones it doesn't. If something on this store isn't right for your machine, we'd rather say so.