There are 72 dowel’s in the pack
If you are planning to join 2 boards (edge to edge) the glue is actually stronger than most wood. You might need some kind of dowling jig to get it right. If you want to attach the shelf to the wall (and really load it down), Home Depot carries a "French cleat" hanger that works really well, though much more expensive than dowel pins. Best wishes and enjoy your project.
The wood our dowel pins are made from is Chinese Cherrywood.
I've used regular doweling to fix stripped out holes and they work great. These should work just as good or better since they are grooved and can grip the hole drilled for them better and have space to hold the glue too.
No. Buy a longer/thicker dowel and cut to the desired length. Something like a 4' long, 3/8" to 1/2" diameter. Cut 4 pieces off at 4". Drill the applicable size hole 2" deep on the posts and you're done.
Neither! The ones I bought mic ed out at 0.23 inches or <6mm. (0.2" is 5mm)
There are 72 pieces in a pack.
The package simply says "made of hardwood"