If you're still printing on the stock glass bed or the original magnetic sheet your printer came with, a PEI sheet is probably the single best value upgrade you can make. It's £10-20, takes five minutes to fit, and it solves bed adhesion problems that would otherwise require hairspray, glue stick, and a ritual to the printer gods every morning.
I used a glass bed for my first year of printing. It worked fine with a thin layer of glue stick and regular relevelling. Then I fitted a PEI sheet and realised I'd been making extra work for myself the entire time. Prints stick firmly while printing, release cleanly when the bed cools, and I haven't needed adhesion spray since.
PEI (Polyetherimide) is a thermoplastic with a surface texture that PLA, PETG, ABS, and most other filaments bond to well at printing temperature and release from easily once cooled. The key property: prints grip firmly when the bed is warm and let go with minimal force once the bed drops below 40°C or so.
Most modern printers now come with some form of textured PEI surface. If yours doesn't, or if the stock surface has worn out, a replacement PEI sheet is one of the most worthwhile things you can buy.
Smooth PEI: Produces a very smooth, sometimes shiny bottom surface on prints. Good for PLA. Can bond too aggressively with PETG - prints sometimes stick too well and are difficult to remove without damaging them.
Textured PEI (powder-coated): Has a fine texture that produces a textured bottom surface on prints. More forgiving with PETG - the reduced contact area means it grips well but doesn't fuse. The textured surface also hides any imperfections in the first layer. Most people prefer textured over smooth for general use.
Double-sided PEI: Smooth on one side, textured on the other. Practical because you can flip it for different materials. Particularly useful if you switch between PLA (textured) and something that needs the smooth surface.
Energetic is one of the most consistently recommended PEI sheet brands in the community. Their double-sided spring steel sheet (smooth one side, textured the other) is what most people recommend as a first PEI upgrade. It's magnetic, so it snaps onto the bed, flexes for easy print removal, and flips for different materials.
Priced around £15-25 depending on size. Available in the common sizes (235x235 for Ender 3, 257x257 for Prusa MK3/4, and others). The texture and adhesion quality are consistent, and it's held up well to extended use.
Best for: Most people. The double-sided design covers PLA and PETG without any additives.
Fysetc makes a solid budget PEI spring steel sheet for around £10-15. Textured surface, magnetic backing, flexes for removal. It doesn't have quite the same consistent texture quality as Energetic, but for PLA and PETG it does the job well and the price is genuinely low.
Good option if you want to try PEI without spending much, or if you need a spare sheet for a second printer.
Best for: Budget buyers, first-time PEI users, spare sheets.
Bambu's own PEI plates are purpose-designed for their printers and the texture and adhesion are excellent. If you have a Bambu printer the official plate is worth paying for - it fits perfectly, works with their AMS system, and the quality is consistently good.
Also available in a high-temperature variant (for ABS/ASA) and a cool plate (for PLA that tends to stick too well to textured PEI). Having two plates for different materials is a practical setup if you print a wide range.
Best for: Bambu Lab printer owners.
Resin printers use a different bed system - an FEP (fluorinated ethylene propylene) film in the resin vat rather than a PEI build surface. FEP films wear out over time and need replacing. If you're having adhesion issues with your resin printer, a worn FEP film is often the cause.
FEP films are cheap (£8-15 for a pack) and replacement is part of regular resin printer maintenance.
The first time PETG bonded too hard to my smooth PEI sheet and took a chunk of the surface with it when I removed the print, I assumed I'd ruined it. Turns out that's a common PETG problem on smooth PEI - the fix is either a thin layer of glue stick as a release agent on the smooth side, or just using the textured side for PETG.
Since switching to the textured side for everything except prints where I want a perfectly smooth bottom face, I've had zero adhesion issues with PLA, PETG, or TPU. The prints stick, they release cleanly, no scraper needed, no glue stick. The textured surface marks are barely visible on most prints.
Keep it clean. Oils from your fingers reduce adhesion. Don't touch the print surface. Clean with IPA (isopropyl alcohol) regularly - before every print session if you want consistent results.
Let it cool. PEI releases prints much more easily at 30-35°C than at 60°C. Wait for the bed to cool before trying to remove a print.
Don't use adhesion spray on textured PEI unless you have to. It works, but over time it can clog the texture and reduce performance. For most materials on textured PEI, the surface alone is enough.
For PETG on textured PEI: A very thin layer of glue stick acts as a release agent and prevents over-adhesion. Wipe it on thinly, let it dry, then print. The print releases cleanly and the surface is easy to clean afterwards.
A PEI sheet is the first upgrade I recommend to any new 3D printer owner. £15-20, five minutes to fit, and it solves one of the most frustrating parts of getting started. Get the double-sided version and you're covered for almost everything.