The stopper is synthetic

It is considered that synthetic (plastic) traffic jams keep freshness and aromas of quickly realized wines more reliably, reducing risk of infiltration of air and oxidation. Synthetic (plastic) traffic jams proved the advantage as insulators for local wines which drink within one year. The synthetic stopper densely corks a bottle and air does not pass, the bottle can be stored in vertical and horizontal position.
GOST P 51958-2002 of means corking polymeric