The ever-shifting Tesla Model S lineup has gone through another change.

It will slim down as Tesla discontinues the electric car's current base models—the rear-wheel drive Model S 60, and the all-wheel drive Model S 60D, both with 60 kilowatt-hours of battery capacity.

Both versions are being pulled from the Model S lineup after less than a year on sale.

DON'T MISS: Tesla adds two Model S 60 versions starting at $66K, still 200 miles or more (Jun 2016)

The decision was made because most customers ended up stepping up to the larger 75-kwh battery option, a Tesla statement said, adding that eliminating the 60-kwh models would "simplify the ordering process for our customers."

Customer who want a new 60-kwh Model S have until April 16 to place their orders.

As before, customers will have the option to upgrade their cars' battery packs to 75 kwh of capacity through an over-the-air software update, for an extra fee.

2017 Tesla Model S

2017 Tesla Model S

Discontinuation of the 60-kwh models trims the Model S lineup down to five variants.

Those are the rear-wheel-drive 75 and all-wheel-drive 75D, as well as the all-wheel-drive 90D, 100D, and P100D.

Tesla's rationale for eliminating the 60-kwh Model S variants is similar to its reasoning for cutting the 40-kwh Model S before any cars were actually produced.

ALSO SEE: Tesla Model S 60-kWh Version: EPA Range Rated At 208 Miles (Dec 2012)

When the Model S was launched, Tesla advertised a 40-kwh variant, but orders were so low that it never went into production.

Instead, Tesla offered a software patch limiting battery capacity of base cars from 60 kwh to 40 kwh.

As with the current Model S 60 and 60D, Tesla offered owners of these cars the opportunity to boost battery capacity for an extra fee.

2017 Tesla Model S

2017 Tesla Model S

Deliveries of the original Model S 60 began in January 2013, several months after the launch of the then-top 85-kwh models.

This version was supplanted in 2015 by 70-kwh versions of the Model S, then reintroduced last year.

CHECK OUT: 2016 Tesla Model S vs original: how do they compare in value? (Jul 2016)

The Model S 70 was in turn replaced by the current Model S 75, which is now the de facto base model.

Until Tesla decides to make another change to the Model S lineup, at least.

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