Opponent used two different rackets

[jtrom]

I did a quick search to see if there was a thread on this in the past and didn't turn up anything.

So during a 3.5 singles tourney event this past weekend. My first round opponent used two different rackets, one during serve games and one during return games. At the end of each game, even if there wasn't a change of sides, he would quickly run and switch out the rackets. This was the first time I had ever seen this before. We had a good close match that he ended up winning. At first, I was just slightly annoyed, but as the match kept going it became increasingly annoying. It was like he was invoking some advantage by having a different racket set up that enhanced serves that I wasn't capitalizing on and therefore getting beat. He seemed to play exactly the same way no matter which racket he had, as his serves weren't that tough to handle. Most of the points ended up in rallies anyways.

I stuck around after our match to see if he would do it again, and sure enough, he was out there switching rackets during his 2nd match.

Is this common/against the rules/should I be doing it??? Does anyone out there also use different rackets within the same match??