How wide is the radian 3R, 3RX, or 3RXT? June 07, 2021 11:00 Updated All models across the Radian 3R series share a width of 17 in. (43.2 cm). If you’d like to find out more about the Diono Radian 3R visit our store: https://store.diono.ca/radian-3r/ Related articles How wide is the radian 3R, 3RX, or 3RXT? Can you recycle Radian car seats? Where can I find information about recalls? Comments 0 comments Article is closed for comments.