Justin Bieber's Concert Boxing Gloves ... Were Made For Mayweather

Even the props on Justin Bieber's tour have swag ... including the boxing gloves he uses in the show ... which were actually custom made for Floyd Mayweather ... TMZ Sports has learned.

If you haven't seen the show (shame on you) Justin does little a shadow boxing during his (very emotional) performance of "I'll Show You" ... and drapes a pair of boxing gloves around his neck.

We spoke to Elvis Grant -- the guys who makes Floyd's $2,500 gloves -- and he tells us the gloves you see are -- or were Floyd's -- created for his mega-fight against Canelo Alvarez in 2013.

Fun Fact -- When a big deal boxer like Mayweather has a bout, multiple pairs of gloves are commissioned in case something goes wrong ... and Elvis tells us Bieber snagged a pair of backups.

Pretty cool ... and ultra pimp considering those gloves are worth around $2,500.