The pair will remain in custody with their sentencing due at a date to be determined.

The trials of Mai Dinh Quang To and Jimmy Cuong Lieu were listed earlier this week, but both subsequently pleaded guilty.

They were initially granted bail after their arrest in August last year before being remanded in custody following bail reviews which indicated they had precursor capable of making drugs worth $7 million.

Tendered facts indicate To, 30, and Lieu, 33, flew from Sydney to Melbourne on August 14 last year in adjacent seats on a plane.

They booked into a motel and To hired a Nissan X-Trail from Budget at the airport with Lieu listed as an additional driver.

There were phone calls between To and another man, who went to a storage shed in South Melbourne about 6.20pm on August 15.

That storage shed was searched by police on September 18 and they discovered 650 jars similar to those found in the possession of To and Lieu.

Their vehicle had travelled along the Melbourne City Link at 6.57pm and they were stopped for speeding near Mullengandra about 10.50pm.

Given permission the check the car, police found a black bag containing seven jars and 32 jars inside each of two cardboard boxes.

The 71 jars were later weighed and examined by Australian Federal Police with the total weight being 70.993 kilograms and 18.4 kilograms was pure ephedrine.

There was no evidence either were involved in the actual supply of a prohibited drug, but were just transporting it.

Their cases have been adjourned to the District Court in Sydney on September 12 for mention.