Geeksphone has begun taking preorders for its latest Firefox OS handset, the Peak+.

The Spanish smartphone startup became the first company to start selling devices running Mozilla's OS earlier this year when it launched two developer handsets, Keon and Peak .

Peak+ improves on the original Peak's specs with double the RAM at 1GB, but share the same chips in the shape of the 1.2Ghz Snapdragon S4 processor, an eight-megapixel rear and two-megapixel front camera, 4GB of memory and 4.3-inch screen.

It does however, according to Geeksphone, have a "superior look and feel" and "premium materials".

While the Peak+ also runs Firefox OS 1.1, Mozilla is at pains to point out it's not an official Firefox OS handset.

"Today, Geeksphone announced the pre-sale of a new device based on Boot to Gecko technology. We want to clarify that this new phone that was announced is based on Boot to Gecko technology with pre-release software, but is not a certified or supported Firefox OS device," the company said.

The Peak+ is priced at €149 during the preorder period (it's expected to go up to a standard price later on) and will ship in mid September. The original Peak, released in April, was also priced at €149. It sold out shortly after it went on sale.

Firefox OS devices first went on sale to the public earlier this month in both Spain and Madrid , where local operators began selling Alcatel-made Firefox OS devices.

Germany and Greece are expected to be the next countries to get Firefox OS handsets.