It's hard to tell from your photos, but it looks like a thin-bladed Miscanthus sinensis like 'Gracillimus' or many others. They'll grow anywhere from 3' to 6' high..maybe 7' to the blooms, depending upon cultivar, conditions and your zone.

Here is another picture:

{{gwi:866649}}

I'm still going with my previous semi-ID, although I think I see some medium-width blades in this photo. It's hard to tell if the fine blades belong to the plant in the front or in the back.

Whatever M.s. cultivar it is, the space you have it in will be too small in a couple of years. It's top will be spilling out over the steps on one side, and the bed edge on the other.

The previous picture I posted had two different kinds of ornamental grasses next to each other. Here is a better picture. What kind is it? Is it going to be like a Gracillimus? I planted it for privacy.
{{gwi:866651}}

Again, it looks like a fine-bladed Miscanthus sinensis, like 'Gracillimus.' It will get full and tall in time (at least 3 years.

It will only provide privacy from about early summer on, though. You have to cut it down early every spring.

Thanks!