Hello,
Thank you for your question.
Both of the beds will take a single mattress 90cm x 190cm, however the underbed mattress does require to be no deeper than 17cm. Please see the links below for mattresses that would be suitable for both the top and bottom bed, you can also add these as a bundle to save money if buying 2 mattresses:
https://www.time4sleep.co.uk/products/europa-comfort-slimline-sprung-mattress
https://www.time4sleep.co.uk/products/europa-ortho-luxury-1000-slimline-pocket-sprung-mattress
Kind regards,
Laura
Time4sleep
From the Time4Sleep team