Seed at the bottom inside capsule
In this model seed is visible . once it touch with water , the capsule will dissolve in water and seed comes out side 

Seed Below the ring
In this model Seed is not Visible, you can feel by touching on it 

Space for Put Seed in Bottom of pen
In Some countries seed are restricted to import.Seed can fixed by customer 

Seed Kept inside the bottom
Inner Diameter if 5 mm . in this model customer can insert seed and just shape it . 

A Pen with Metal Refill after Crush the paper 

A Pen with Plastic Refill After Cutting with a Blade 

Pen planted to soil Sprout will come in 3-5 days

Sprout from cap