The club is returning to the Champions League for the first time in over 20 decades, Newcastle United have worn the home kit that has no stripes on their backs in contrast to those who wear their Premier League home kit. We will find out why.

CHAMPIONS LEAGUE NEWCASTLE UNITED HOME KIT

This Newcastle United Champions League home kit is the same as that of the Premier League home kit, with the exception of those stripes that are on the rear.
The reason Castore was required to take off the stripes on his back shirt was due to UEFA Equipment Regulations.

This makes it easier for TV viewers and fans to determine the players’ shirt numbers.

However, the season’s Barcelona shirt does not require the stripe on the back of the shirt to be removed. Why?
The answer lies in the regulations of UEFA’s “Measurement and contrast of colors”.
The past was when Inter had no requirement to take off the stripes from their jerseys since they continued to provide the necessary contrast as required by UEFA regulations.