These 1.5" starter plugs from Grodan are great for seed starting or rooting clones.
Grodan's Stonewool (Rockwool) starter plugs are made from molten basalt rock and chalk that are spun into fibers and then formed into blocks, cubes or slabs. It can hold up to 80-90% of its volume in water, yet leaving plenty of air space for root growth. Excess water will drain easily away. the A-Ok starter Plugs come in a sheet of 98.