How wide is the radian 3R, 3RX, or 3RXT? June 07, 2021 11:02 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 3RXT visit our store: https://store.diono.ca/radian-3rxt/ Related articles How long can I use the radian 3R, 3RX, or 3RXT in booster mode? Where can I find information about recalls? Will Diono remove flame retardants from their all-in-one convertible car seats? Radian RXT (Manufactured prior to May 2016) Radian 3RXT Comments 0 comments Article is closed for comments.