Free Delivery. Free Oficial Case. What does the i stand for in the new SR225is from Grado? enhanced, that’s what! Features are the same as the SR125is, new driver, cable & housing designs, but this headphone has an increased rear air flow, utilizes Grado’s larger ear cushion & has closer matched drivers. Air flow is increased by 50% which is achieved through an enhanced rear metal screen. The use of closer matched drivers & the larger cushions results in an enlarged soundstage, while the enhanced rear screen frees the headphone from colorations.