Hello,
I'm thinking of buying this module to use with Arduino (5V)
https://www.ebay.es/itm/A6-GPRS-Pro...520106?hash=item1a4055e2aa:g:moUAAOSwMGVaVzB6

In the description it says: "Interface logic voltage: 3.3V". It has its own power regulator.

My question is: is 5V tolerant the interface (rx, tx) of this module?

 

hi 92,
Checking the specification I would say that the module requires a 5V/3.3V level shifter between the Arduino and Module UART lines.
If you Baud rates are low, I have used 2k/3k3 resistive level shifter for sending to GPS module and a 10K pullup on the GPS output line.

E
EDIT:
I use these modules for faster transfers, will run at 20MHz on SPI.

https://www.amazon.co.uk/MagiDeal-C...=8-3&keywords=5v+to+3.3v+level+shifter+module