Promise ring

So we've been talking about a promise ring for the longest time and we've been together for almost 7 months now and I thought it would be a great gift for our 6 month so he told me we should go to the jewelry places and I'll give him an idea of what I want and he'll pick it out. Well he kept saying he didnt like any of them but the thing is is he went shopping for a tux for prom the day before and already picked out a ring with his mom and he surprised me with it!! I love him!