The effects of kratom are often compared to opium (though milder and not as addictive), and this block of resin even looks like it. The resin can't be smoked however, it needs to be dissolved in hot water.
This "resin" (actually a condensed paste) is produced by boiling down kratom leaves in water until a thick, sticky substance remains.
Each piece of kratom resin has an average weight of 5 grams. *
1.5 to 2.5 grams is sufficient to get a satisfactory experience.