Last year Lollapalooza became the first major US music festival to use radio frequency identification (RFID) technology to allow concertgoers to more easily pay for things like food and beer.

Using a small embedded chip inside the festival wristband, the program, called Lolla Cashless, allows attendees to register their wristbands online and link them to a credit to debit card. Then, when purchasing an item at the point-of-sale system, fans just tap their wrist to the machine to pay. The idea is that you can leave your wallet at home, and not worry about the risk of losing your cash at a crowded festival.

Lollapalooza brought the RFID technology back for a second year, and a spokesperson gave us the lowdown on just how many people were using Lolla Cashless. At this year’s festival there were 55,222 registered Cashless users, compared to 43,575 in 2014, a 28% increase year over year.

So assuming around 300,000 people attended this year’s festival, just under 20% used Lolla Cashless.

Since 2014, RFID wristbands have also been used to pay for goods at the Low Festival in Spain and Austin City Limits.

The Lolla Cashless spokesperson didn’t immediately respond when asked how much was spent using Cashless or how frequently it was used, but Billboard reported in 2014 that Cashless generated a third of overall concession revenue at last year’s festival.

Judging by some of the reaction on Twitter, it looks like Lolla Cashless worked well for some festivalgoers, maybe even too well.