There are 3 Practice Chanter reeds documented here .... the 2 PC reeds in the photo (PC Reed & Straw Reed subpage), and a detailed guide on making a wide-bladed PC reed that can also be lengthened and used for Small Pipe chanters (see Plastic PC Reeds subpage).

Well .... the dimensions haven't actually been written up yet .... but here's the description:

These GHB drone reeds are a completely original design; made with ABW bodies and carbon fiber tongues they are rich and bold! While the design is 100% original, it was influenced by this article on Tim Britton's UP dowel drone reeds, and an internet post discussion on Rocket Reeds, and benchmarking tone against a custom set of Murray Henderrson's Harmonic drone reeds.