Custom design your diamond engagement ring with us Custom by Z has over 25 years experience designing and working with GIA certified stones. N.J. Diamonds has a GIA diamond grader onsite. We use Cad Cam technology to assist when designing your diamond engagement ring. At N.J. Diamonds we always work with the budget you do not want to exceed. We service our diamond jewelry for life free of charge. Work with the best when you want to design your perfect diamond engagement ring N.J. Diamonds custom by Z is here to work with you every step of the way.