YOPIN Soundproofing Sheet 30x30cm, 2mm Thick, Approx. 3.5kg/m2, Sound Insulation Sheet

Selling because I accidentally purchased double the amount on Amazon.
Immediate purchase is welcome.
Price is firm. I will consider lowering the price if I receive many likes.

Can also be sold individually in sets of 30 for 6700 yen.

The following is copied from Amazon:

Item Quantity: 1
Brand: YOPIN
Item Thickness: 2 mm
Item Dimensions: 34 L x 34 W cm
Manufacturer: YOPIN

[2mm Thickness] Soundproofing effect is influenced by the surface density of the soundproofing sheet. By increasing the thickness to 2mm and achieving a surface density of 3.5 kg/㎡, the soundproofing effect is doubled compared to general soundproofing sheets. Excellent sound insulation performance with an acoustic transmission loss of 23dB at 1000Hz. It also does not cause radio wave interference (disruption of wireless LAN or mobile phone signals).
[Easy Installation] The soundproofing sheet size has been improved to 30cm x 30cm, weighing only 0.315kg per sheet. This convenient soundproofing measure can be easily installed even by non-professionals. It solves problems such as large area makes installation difficult, cannot cut properly, and waste due to lack of appropriate size.
[Safe Material] The soundproofing panel is made of soft PVC material, which is eco-friendly and flame-retardant. Furthermore, its high density provides excellent waterproof and moisture-proof properties, ensuring safe use.
[Wide Range of Applications] When used in combination with compatible sound-absorbing materials (sold separately by our company), it can achieve synergistic effects for significantly improved sound absorption and soundproofing performance. It can be used in various situations such as rooms, audio rooms, studios, home theaters, apartment soundproof walls, and car sound deadening.
[Quality Assurance and Notes] If there are any issues with the delivered product, please contact us with reference to the instruction manual. We will respond with sincerity. Please note: The rubber smell may be noticeable at first. If you leave the product in a well-ventilated place for about a week, the smell will diminish. You will need to prepare a staple gun separately for installation.