A month before opening day, Metro officials yesterday displayed four new rail stations on the planned Red Line extension stretching along Montgomery County's booming Rockville Pike corridor to the Shady Grove terminus near Gaithersburg.

The seven-mile extension, scheduled to open Dec. 15, will mark the second major expansion of the Red Line this year. "Growth is the name of our business," said Theodore G. Weigle Jr., the transit authority's newly appointed deputy general manager, as a train sped north.

The extension, which includes the White Flint, Twinbrook, Rockville and Shady Grove stations, has been largely ready for nearly a year, but its opening was delayed because of a shortage of rail cars.

When the extension opens, the Metro system will include 60.5 miles of tracks and 57 stations, well over half the 101-mile network envisioned by local officials. The Red Line was extended 6.8 miles in August from the District's Van Ness-UDC stop to the Grosvenor station north of the Capital Beltway.

During yesterday's tour staged to publicize the new $278 million extension, speechmaking was curtailed because of chill, breezy weather. "It's cold out here," said Metro General Manager Carmen E. Turner as she launched the two-hour excursion at the skylight-roofed White Flint stop.

The Shady Grove station, which is near Shady Grove Road and Frederick Avenue (Rte. 355), overlooks two sprawling parking lots with a total of 3,100 spaces -- more parking spaces than any Metro station. Metro plans to offer free parking at Shady Grove for the first three months to entice commuters.

White Flint, Twinbrook and Rockville also have sizable lots. Parking will cost $1 a day on weekdays.

Montgomery County officials pointed to major improvements in streets to provide access to the new stations, along with plans for expanded Ride-On bus service to the stations, starting in January.

While the new stations appeared virtually complete and yesterday's train trip seemed flawless, Metro and Montgomery County officials said that several construction projects remain.

At the White Flint station at Rockville Pike and Marinelli Road north of White Flint mall, plans for a second Metro parking lot with 500 more spaces have been delayed because of negotiations with developers. The existing Metro lot provides 930 spaces, officials said.

At the Twinbrook stop near Twinbrook Parkway and Rockville Pike, a special entrance ramp for elderly and handicapped patrons needs to be rebuilt because it slopes too steeply, officials said.

At the Rockville station, a glass-enclosed overpass designed to allow patrons to cross congested Hungerford Drive (Rte. 355) is not open because of a major redevelopment project at the old Rockville Mall.

Yesterday, Montgomery County transit services chief Edward A. Daniel was asked if he had any regrets about the Red Line extension.

"I wish we could have built it faster," he said. "I wish we could have opened it five years ago."