Connecting to the Era 100 line-in will have an unavoidable 70msec delay in the audio, which results in lip-sync issues. Most find this lack of sync too distracting. Sonos soundbars reduce this delay, hence them as the recommended devices for home theatre systems. 
That doesn’t directly answer the question, but might make it moot? 

Thanks, it will not distract me 

just wanted to know if I can use this accessory on my era 100

Unless I’m mistaken, USB-C cables are all the same design, otherwise they can’t be called USB-C. 
 

Whoa, wait.  The USB-C port on the Era 100 is an input, not an output.  If your intention is to connect the Ace to the Era via USB (or even via 3.5 mm analog) in order to listen to the Era content on the Ace, it’s not going to work.

Ah. Perhaps I misunderstood the question. ​@jgatie is absolutely correct. USB-C is indeed USB-C, but line ins are not the same as line outs. 

Hi ​@Gualandi0 

Welcome to the Community!

Thanks for your question, but I feel a little clarity is needed here.

Yes - the 3.5mm to USB-C cable that comes supplied with the Ace headphones can be used for a line-in connection to an Era 100 (or Era 300, or Move 2), bypassing the need for a Sonos Adaptor.

In addition, the Sonos Adaptor can be used as an (unrecommended) alternative to the Ace’s supplied cable (though a 3.5mm to 3.5mm cable would be needed too).

As the others have rightly (but superfluously) stated, you cannot use the cable to listen to content the Era is playing on your Ace headphones.

I hope this helps.

It’s for a line-in not a line-out

thanks for your responses