Yeah I know there is a Forum topic that is similar to this, but I had a line for it, especially if you do own the DF 500 DOMINO, but evidently I have been blocked by the less than adult, Master of that link. I won't lower myself to say more about that.
I had ordered some hose connectors to a few sizes of tools with really strange sized dust ports from these guys, got exactly what I had hoped for, quick, and well made, for just a fraction of the aggravation they would have been to try to make melting PVC and such. In the process I got on their email list.
I really hadn't heard from them since, the other day I got an email saying they were offering their slide on conversion tool to take a DOMINO from metric to US imperial sizes. So if you are like me, and don't own any MM tape measures, and don't typically use MM measure, then you my be interested,
The gauge is free, you just pay it's shipping? Here I suggest asking them how much before you order, I say this because it still says shipping is free USPS regular shipping, so I'm not sure how much they will charge, should show in a cart before you pull the final trigger I would think.
Anyhow details are on the link to page. If you want the free DOMINO gauge put it in as Coupon Code: FREE-DF-500, and it will be either added to an order, or just be an addition, then is when I think they would charge you on shipping. They are an Ohio company, so if you are in Calif, or Hawaii, Alaska, it could be more than to me, also in Ohio. You would have to check it out.
Writing this out, and looking at their page I also got some MDF like inserts for the Sawstop CTS I bought for my Wife to use. They are really nice. Look and feel like MDF, but coated with something wax like, that makes it do ok if it gets wet. At least a little bit wet. MDF is like a sponge, this is not, also seems pretty strong.