To find icons in specific sizes you can use the slider for Icon Size on the left-hand side of the search results. By moving the slider, you can filter out unwanted sizes.
Currently, you can filter sizes between 0 and 512 pixels. You can preview how the icons will look like, as they automatically resize when you move the slider. If you have found an icon you like, you can also select the size from the horizontal bar just above the icon. You can also preview how the icon will look like i different sizes and choose the best one for you.
You can also filter by Format, License type and choose the desired Background.