Extendable toddler bed

[SAF55]

I want to buy an extendable toddler bed to grow with my two year old. I’ve seen a few and think I’ll go with the ikea one, but which size mattress do you get? Safe bet and go for a middle size and then size up as you extend the bed or put the bed on full length and full size mattress already? Any recommendations of beds also appreciated!

My DSis had one of the naice IKEA ones for my DNephew and she bought the corresponding IKEA mattress which comes with different 'slices' that you zip together as the bed extends. I think the iron-frame ikea bed has three different lengths, so the mattress comes in three pieces. I'll have to check with her as it's getting passed on to DS!

Here's the link to the mattress- https://www.ikea.com/gb/en/p/innerlig-sprung-mattress-for-extendable-bed-80348596/

Thanks so much, have now seen it on the website! Not sure why it wasn’t coming up as a suggested mattress when I was looking at the bed.