This is probably not a recommended toy to use as a tail-holder. The glass, being hard and unyielding, would likely start to get uncomfortable after only a short amount of time. It's also a wand or dildo, meaning it's quite long, and may end up disrupting things internally if worn as a plug. The non-flared (not to mention heavy) nature of it will probably also make it difficult to hold it in for extended periods of time. Plus the nubs would probably start to irritate your tender flesh, and the heart would be too large and bump into things or show under your clothes. Not really a good choice in any respect.
I recommend a silicone butt plug like the Ryder
, which many people have reviewed to be a comfortable long-term wear plug. Others who do use a harder material reach for things like the Pure Plug
, which is metal. The Pure plug has a handle like the Rainbow Heart does, so you can still attach your tail the way you intended.
If you're stuck on using glass, I'd recommend probably using the Fashionistas Small Bunny Tail butt Plug
, which already has a tail attached, which you can probably modify to hold your tail.
Hope this was helpful, please be careful with your body and play safe!