Grodan is a sterile and very versatile media with an excellent air to water ratio for optimal plant performance.  Grodan is very popular with Lettuce and Herb growers as it leaves no "gritty" bits in your salad.  These cubes of 25mm x 25mm x 40mm are idea for propagation of seedlings or cuttings. Each has a hole for seed placement. 

Sheets of multiple cubes can be placed on an Ebb and Flow propagation table for high density propagation.  After germination they can then be transplanted directly into an NFT channel, moved on into the larger cube for growing on, or placed into a growpot and surrounded with media such as pumice, scoria, or vermiculite.

 1 x grodan slab 25x25x40mm = 200 cubes