Pre engagement rings are similar to promise rings because both of them signify some form of commitment and are given in romantic relationships.
In either case, the commitment is a promise to uphold a monogamous relationship. However the difference is that the pre engagement ring is just that, it's a ring given that says "we intend to get engaged".
While a promise ring simply takes a young couple's relationship to the next step without necessarily committing to a future engagement.
Birthstone promise rings are by far the most common and can be worn on any finger since the commitment is to the relationship and doesn't necessarily suggest an intent of a future engagement. However, pre engagement rings do, and are usually worn on the ring finger of the left hand.
In order to minimize any confusion with an eventual engagement ring, some choose to wear it on their middle finger or index finger, or even on the ring finger of their right hand instead.Although these rings are mostly given to women by the men they are dating, some women choose to give them to their men as well, as a symbol of their personal commitment and the trust they have towards the relationship. This exchange of promise rings symbolizes the seriousness of their commitment.
On the other hand, pre engagement rings are usually given to the women solely as a precursor to an engagement ring. They specifically suggest that an engagement ring will be coming and that his intentions are towards marriage.
Both pre engagement and promise rings are usually found in the relationships of younger couples since they aren't likely to be mature enough to marry or in a position financially to commit to a wedding and marriage.
In terms of style and design, the rings usually hold some form of symbolic representation or sentiment including heart motifs to represent love, small diamonds to symbolize a future wedding engagement, and even inscriptions of love or the couple's names. Claddagh rings (like the one in the picture at the top of this page) are particularly appropriate due to their symbolism and the heart and hands details.
Birthstone and gemstone rings are also quite popular and can mark the birth month of either person, or the month in which the couple met, or the month in which they committed to each other.
Since these rings are all about a couple's relationship rather than part of a formal tradition, the options for them are endless and usually come down to a question of budget. Our only suggestion would be to stay away from a diamond solitaire setting since that ring style could lead to confusion.
Given the subtle differences between promise rings and pre engagement rings it's important that the person giving the ring is clear on what they're offering.
If it's a promise to uphold a monogamous and committed relationship as opposed to an intent to get engaged and marry, then that needs to be clearly understood by the recipient. So make sure you make your intentions clear and that she knows what you're giving her.