trx suspension straps

I don't have rings but i have trx suspension straps.

Is this good substutition?

Depends on what you're doing. It's should be fine for Foundation. The flat grip might interfere with false grip training, though.

I am curently on foundation 1.

For rope climbing progression i first used a straight bar but then i get trx so i will try with them now.

Yeah, you should be fine up until R1. 

Ok thanks.

For F1 no problem. May air may not work for later elements in the series, due to the straps being sewn together rather than two separate straps. But I'm sure by the time you get to that point you'll have worked it out on your own.