steriliser question

my friend has been using an avent steam steriliser the last few weeks since birth of her baby. her partner threw out the tablets needed to clean it what are these tablets called and where would you buy them, curious myself as would like to have them got for our tommee tippee for december thanks

They are just a descaler I ran out so bought the sachets for cleaning your kettle in the supermarket. Just make sure it's rinsed out afterwards

thanks twinkles!!