Very lousy plastic, space bar generated clunk, clunk sound, but otherwise nice wireless keyboard if you don't care much about quality of plastic.

Protocol documentation

• logitech_hidpp_2.0_specification_draft_2012-06-04.pdf from http://6xq.net/git/lars/lshidpp.git/plain/doc/logitech_hidpp_2.0_specification_draft_2012-06-04.pdf

Linux software

• https://github.com/pwr/Solaar