If you read the comments from Antonio Mazzatenta concerning this set, you have been given very misinformed information.
1) The singles presented in this collection were NOT recorded in stereo! Each song was multi-tracked, meaning, each was recorded on two, three, four, or more separate tracks, with instruments on some, and vocals on others, then mixed all together to form a final mono track that was pressed on vinyl records and copied to consumer tape formats. This means that the same sound information comes out of each speaker the end-user has. This also avoids things like phase cancelletion, and is not vulnerable to the peculiarities of the listener's stereo system.
2) The reason the music was mixed for mono for the 45 R.P.M. singles was so that they would sound their best on mono AM radio, or the millions of mono record players people used in the 60s.
3) It isn't just a case of mono vs. stereo. The mono mixes were usually different in several ways, from having different musical parts and/or vocals than the stereo, to different EQ and echo that was applied. Many of the mono singles ran longer than the stereo counterparts.
4) The mono mixes were done first by the main session engineers and/or the producers. The stereo mixes were done as an afterthought for the albums, and many were done by a nighttime engineer, literally in the house next door!
5) The stereo mixes are available everywhere. They are usually the mixes found in the stores. The mono mixes, because of several factors, have rarely been reissued, and usually found on pricey boxed sets, and not commonly found. Many fans, as a result of the push for everything stereo for decades, have not even heard the original mono 45 mixes they heard back in the 60s and early 70s. The mono mixes were the mixes that were the hits, the ones people bought in the stores, heard on the radio, and were the ones that raced up the charts. They were special, and the ones that the producers and engineers labored over for days and weeks. The stereo mixes, were usually done in a matter of minutes, and their relative lack of quality showed for it, too.
I get tired of hearing the "we have two ears" argument. Those who like to say this ignore the fact that most mono singles were mixed differently than the stereo mixes in terms of instrumental and vocal differences.
If you want to hear these hit recordings the way you remembered them, sounding their best, buy this box! Listen to the songs and the memories will flood back to you in a way that the stereo mixes could never do for you.