Yep - the caps perfectly! They aren't the same model though - Blu is a L88B and Sidesho is a J108. Some parts are compatible, some parts aren't. Check out the Modern Vapor sub-forum. You'll find out what is and isn't compatible. Answers to all your questions should be there. And if not - ask Tony - he's a great guy to deal with.
I have about 100 caps. I fill a week's worth at a time and put them in an embroidery floss box. All the convenience of using stock Blu carts, without the expense and limited flavor selection.
Another tip - pick up a Brother P-touch label maker (I got one for $10 on eBay) and the thinnest tape - smallest font, vertical alignment, and two letter abbreviations for flavors - looks exactly like the stock carts.
And don't forget Fluval for restuffing the carts. The performance is improved tenfold.
~A