Boys & Their Toys

I'm a boy (well at least mentally) who loves a Toy or a Gizmo to play with, and I treated myself to this 5-Pronged Gardening Hole Punch Seeder off ebay that arrived today!  

The information one really wanted was what I have created above, what's the centres of the prongs, how deep are they, and what's the diameter of the prong at the top. All measured off the one that arrived today. 

They come in Green £5.65, Orange £5.85 and Yellow £6.17