flight in May 1961, the Mercury pressure suit underwent several changes to incorporate improvements, mainly for comfort and mobility. These changes included: Incorporation of wrist bearings and ring locks on the sleeves starting with Grissom's MR-4 suit. Alan Shepard's MR-3 suit had gloves that were zippered onto the suit itself, preventing the astronaut from easily rotating his wrists to control the spacecraft's controllers. Incorporation of a urine collection device (UCD) starting with the MR-4 suit. Shepard, going through long countdown delays, had had to urinate into the heavy cotton underwear in his suit; the engineers had felt a UCD was not needed because the flight itself was to last only 15 minutes. Incorporation of a convex mirror, dubbed the "Hero Medal," on the chest of the astronauts so that the same onboard camera used to record the astronaut could also cover the instrument panel, eliminating the weight of a separate camera which had been used for this purpose on MR-3. This was eliminated beginning with MA-8. After the near drowning of astronaut Gus Grissom during recovery operations after the MR-4 a small inflatable life vest was worn on the astronaut's chest. In preparation for the final Mercury mission, flown by Gordon Cooper, the suit underwent the most modifications, most notably the replacement of the leather boots with ones incorporated directly into the suit. Other changes were made in the shoulder construction, along with the pressure helmet. A new mechanical seal for the faceplate eliminated the need for the small pressure bottle and hose, and incorporated new microphones and an oral thermometer; the latter eliminated the rectal thermometer used on prior flights. Cooper wore neither the convex mirror or the life vest. Shepard, who was Cooper's backup, had an identical flight and backup suit for the mission, and was to wear the modified suit for the cancelled MA-10 flight. MA-9 was the last flight of the Mercury pressure suit. Later use After Mercury, the pressure suit was used for the early development phases for the Gemini program, but because of the success of the X-15 high altitude pressure suit, the bigger room on the Gemini spacecraft, and the need to develop a suit for Extra-vehicular activity (EVA) outside the spacecraft, the Mercury suit was phased out of NASA service and was replaced with the basic G3C version of the X-15 suit. Since then, NASA has used either the David Clark Company,