When getting to the finer art of honing straight razors one moves to higher grit stones, compounds and sprays, the latter comes in various grits and formats and it is advised not to mix the various products on the same leather strop, balsa wood or canvas strop.
I started using leather strips on our aluminium base fairly recently and prefer them over felt strips as I get a quicker results than with felt. The harder the surface of the medium used, the quicker and better it works. The dark brown leather also has a solid consistency and keeps the diamond spray on the surface in a visible state, this helps as you can now detect if there is still enough compound/dust on top of the strip to do the job, this is more difficult with felt that has voids where diamond spray can pass through and sit below the working surface, the grey colour also makes it more difficult to spot a 'saturated' or ready-to-work surface.
Try keeping your leather strips in individual plastic bags or envelopes, its quite frustrating when you discover debris on a strip of leather has just put a nice deep 'scar' on your blade right at the final stage!. I place mine face down in separate plastic bags, and have marked them 1, 0.5 and 0.25 respectively for the different microns diamond sprays I use.
Give these bad boys a go with the diamond sprays, this is a very quick, very effective way to refresh a dulling blade in a minute or two!