The Osprey Nib-Block Kit includes the nib-block, a small plastic dowel, a rubber grip, Silicone grease tube (used to prevent small leaks)  along with G Nib Maintenance Guide that provides tips on Inks to be used, step by step instructions on disassembly and assembly of the G Nib, along with Ink filling instructions.

The nib block itself is nothing but an improvised use of a regular thread spool. If you have one at home, you can use that instead. But note that this kit gives you other tools to maintain your G Nib.

These convenient accessories allow safe and quick swapping of friction fit/ heat-set nibs.  They work with the Osprey Zebra G and  Size 5.5 ultra-flex nib units. 

Osprey Size 6  Regular  and Ultra-Flex nib units  are all  fitted with a feed that has an end tail, and should not be disassembled using  this nib block to avoid fracturing the end tail, instead use the soft rubber grip provided in this kit to pull out the nib and feed from these units.