Brake bleed clear tubing, inside diameter???

Fishey

Yes, I don't know anything about cars because I don't advise gravity bleeding.

First, gravity bleeding uses gravity to flow fluid meaning that there is very little pressure exerted on the line with very little flow. Small bubbles can still stay in the line.

Second, with such little flow/pressure if you have any air in your ABS system it is almost guaranteed not to work.

Third, you don't actuate the master cylinder and you can still have air stuck in it. I have seen this a number of times even with motive pressure bleeders failing to bleed out the brake system properly especially on older Porsche. (964/993) The motive method is like 99% better then gravity bleeding regardless.

Fourth, Running expensive fluid? Cause gravity bleeding tends to be a big waste. I guess unless I am running around watching each bleeder and then closing them but that seems like more work then bleeding properly. I mean most cars hold about 500ml of fluid so wasting half a bottle of SRF does not sound appealing.

Fifth, Gravity bleeding takes forever simply because of the lack of pressure.

So yea....