A ROM card that uses the popular DIP 28 EPROM up to 64KB can be installed
 
ROM product number, ROM program capacity that can be flashed (backward compatible)
27C64, 8KB
27C128, 16KB
27C256, 32KB
27C512, 64KB and Dual 32KB ROM Mode

Comes with Dual 32K ROM Mode. This can be used by switching between two programs with a capacity of 32KB.

Read more detail is here*Assembly, pin setting, etc:
https://ameblo.jp/keroxiee1016/entry-12809570749.html
 
Bare PCB: card only
Price 8USD
 
Kit: Bare PCB card, 2 resistors, 2 capacitors, LED, Slide Switch, 1X5 pin header, 2X4 pin header. *Includes all necessary parts except 28pin IC socket and EPROM(both procure your own).
Price 11 USD
Although not directly related to our store, here are some examples of IC sockets:
https://www.digikey.jp/short/w0bp13n9

Half Assembled: All chip parts soldered(Resistor x2, Capacitor x2, LED x1), all you have to do is solder the pin headers, switche and IC socket(procure your own).
Price 15 USD
 
Fully Assembled: EPROM is prepared by you and flashed by yourself. *Because of the thickness, it cannot be sent by a cheap shipping method.
Price 19 USD
 
Information about the shipping method *Please be sure to read it:
I thought the key to selling this would be how to make the shipping cost cheaper. We sold the same Bare PCB RAM card in a kit some time ago, but we thought we could offer it at the same low price.
The bottleneck is the region, but I think there are many MSX users mainly in Europe. Considering sending from Japan, customs will reject items other than card items. So this time the thick IC socket is not included. The IC socket has 28 pins with a pin spacing of 15.24 mm. You can buy it locally. It's probably about 1 USD per piece at most.
Shipping cost is 7 USD all over Europe with a tracking number. Up to two cards can fit in one envelope. More than that will be sent by UPS or Japan Post EMS.
In the case of a finished product, we cannot send it by a cheap shipping method. It will be an ordinary international courier service (UPS or Japan Post). Please note.