Wen 2307 Rotary Tool - Help needed Answered

Hi there everyone,

I need a bit of help if available.

I purchased a WEN 2307 101-piece rotary tool set from Amazon.ca a few weeks ago and followed that purchase with a Flexible Drive shaft.  Although I was able to attach the drive shaft to the tool, the bits that came with the WEN don't seem to fit the collet of the drive shaft properly.  Therefore, I am planning on returning the drive shaft and purchasing a different unit from a different supplier on Amazon.
The unit that I am considering is an SPTA Electric Grinder Flexible Flex Shaft Rotary Tool Attachment 42" Length and Rotary Accessory which states that it fits All 1/8" rotary tools.

Of course, the drive shaft didn't come with a manual, so I figured out myself how it is supposed to attach.

I'm not very familiar with rotary tools and purchased this unit as a beginner, instead of spending a lot of money on a really good Dremel. That being said, I would like to know if the size of the collet is equal to the same size bit.  (i.e., if the rotary tool is fitted with a 1/8" collet, do you use 1/8" bits, or do you use a different size?

I know that this seems like such a stupid and/or easy question to most people, but, being a beginner, this can be quite confusing.

Any assistance that you can offer will be greatly appreciated.

Thanks