Dell Studio XPS 16 SSD upgrade question

Any 2.5" SSD will work -- that said, you may need a spacer, as your hard drive is 9.5 mm and the  SSD will be 7 mm.  Some drives (Crucial, Samsung's kits) will include the spacer.

If I get a Seagate Hybrid Hard Drive which is 7 mm, would it fit without a spacer or I would still need to get a spacer? 

You'll likely need the spacer.  That said, while a hybrid will be faster than a conventional hard drive, don't expect SSD-like performance - there's a world of difference between an SSD and an hybrid SSHD.

Thanks again. Since I plan to donate this to a family member, I rather not spend a whole lot on an SSD. So a hybrid drive would be the best and cheapest solution. Can you or anyone else recommend a spacer since bare drives don't come with one?

anyone else recommend a spacer since bare drives don't come with one?

Anyone?

You need something like this:

< >

There are others around as well.