Transcend JetDrive Storage Expansion

Hi everyone,

I had a question about the Macbook Pro (Retina, 13-inch, Early 2015) and it's expandable hard drive. I am aware of the Transcend JetDrive and that is the most popular item to use with the Macbook Pro. I just wanted to know if there are other alternatives than the Transcend JetDrive? Because I have the 13-inch, am I only allowed to get the 128GB storage expansion or can I get the 256GB? Any comments or concerns would be a great help! Thanks again community!