Tung-Sol Gold 12AX7 / ECC803S, Matched Pair

any reason not to use in my bass amp?

are these the cryo versions as when they come back in stock (curently unavailable at writing) i plan to buy these for my ugraded version yaquin ms-23b

Will these work with Yaqin MS-23B preamp? The tubes that came with it are 12AX7

Will these tubes work with a pro-ject tube box ds2 phono preamp?