Intro

Different websites provide different specifications for quick couplers, so here we try to reconcile.

Specifications

3/4" NPT ISO 7241-B ouplers. Body size equals thread size. 40 GPM (bought from Industrial Supply Inc are quite large). 40 GPM here [1] is defined as 2 bar pressure drop. 48 GPM for 4-fold power cube is 3-4 bar drop.
ISO 7241-A - Body size appears to equal thread size.
ISO 5675 -
Pioneer 4050-4 - appears to be 12 gpm - [2]

$16 for 40 GPM hydraulic quick couplers - [3]
Safeway S56-6 - 28 GPM - http://www.safewayhyd.com/s56.htm
Safeway S21F-6http://hydraulics.safewayhyd.com/item/agricultural-quick-couplings-s20-series/s20-male-tip-half-nipple/s21f-6-1
http://www.automation-dfw.com/pdf_pneu/tema02-hydisostdprofile.pdf
3/4" ISO 7241-1 A Hydraulic Hose Quick Disconnect Couplers 600-12-12S - 6600 Series - http://www.automation-dfw.com/pdf_pneu/tema02-hydisostdprofile.pdf - $25 on Ebay - [4]
3/4" ISO 7241-1 B - specs - [5]

Parker/Pioneer 4050-5 Female, 8010-5 3/4-14 NPT Female - 12 gpm or 50 gpm? - [6]