The big themes of the second quarter are strong growth in line with our expectations and robust free cash flow, either after the step up in our capex, positive industry indicators, including a strong used-equipment market, where pricing was up 7% year-over-year.
This is timed to the broad based recovery in demand and our focus on operational discipline, as we manage the increase in both volume and capacity, while driving fleet productivity of nearly 18%.
Another key takeaway our safety performance and I'm very proud of the team for holding the line on safety with another recordable rate below 1, while at the same time managing a robust busy season and on-boarding our acquired locations.
When we surveyed our customers at the end of June, the results showed that over 60% of our customers expect to grow their business over the coming 12 months, which is a post-pandemic high.
And notably, only 3% saw a decline coming over the same period.
It confirms our return to growth, including our 19% rental revenue growth in the second quarter.
Our Specialty segment generated another strong performance with rental revenue topping 25% year-over-year, including same-store growth of over 19%.
This year, we've opened 19 new specialty branches in the first six months, which puts us well on our way to our goal of 30 by year-end.
Rental revenue for the second quarter was $1.95 billion, that's an increase of $309 million or 19%.
If I exclude the impact of acquisitions on that number, rental revenue from the core business grew a healthy 16% year-over-year.
Within rental revenue, OER increased $231 million or 16.5%.
The biggest driver in that change with fleet productivity, which was up 17.8% or $250 million, that's primarily due to stronger fleet absorption on higher volumes in part as we comp the COVID-impacted second quarter last year.
Our average fleet size was up 0.2% or a $3 million tailwind to revenue and rounding out OER, the inflation impact of 1.5% cost us $22 million.
Also within rental, ancillary revenues in the quarter were up about $65 million or 31% and rerent was up $30 million.
Used equipment sales came in at $194 million, that's an increase of $80 million or about 10%.
Pricing at retail in the quarter increased over 7% versus last year and supported robust adjusted used margins of 47.9%, and that represents a sequential improvement of 520 basis points and is 190 basis points higher than the second quarter of 2020.
Used sales proceeds for the quarter represented a strong recovery of about 59% of the original cost of fleet that was on an average over seven years old.
Adjusted EBITDA for the quarter was $999 million, an increase of 11% year-over-year or $100 million, that included $13 million of one-time costs for acquisition activity.
The dollar change includes a $141 million increase from Rentals and in that, OER was up $125 million, ancillary contributed $10 million and rerent added $6 million.
Used sales were tailwind to adjusted EBITDA of $12 million and other non-rental lines of business provided $6 million.
The impact of SG&A and adjusted EBITDA was a headwind for the quarter of $59 million, which came mostly from the resetting of bonus expense.
Our adjusted EBITDA margin in the quarter was 43.7%, down 270 basis points year-over-year and flow-through as reported was about 29%.
Adjusting for these few items, the implied flow-through for the second quarter was about 46% with implied margins flat versus last year.
I'll shift to adjusted EPS, which was $4.66 for the second quarter, including a $0.13 drag from one-time costs.
That's up $0.98 versus last year, primarily on higher net income.
For the quarter, gross rental capex was a robust $913 million.
Our proceeds from used equipment sales were $194 million, resulting in net capex in the second quarter of $719 million, that's up $750 million versus the second quarter last year.
Even as we've invested in significantly higher capex spending so far this year, our free cash flow remains very strong at just under $1.2 billion generated through June 30th.
Now turning to ROIC, which was a healthy 9.2% on a trailing 12-month basis.
Year-over-year, net debt is down 4% or about $454 million.
That's after funding over $1.4 billion of acquisition activity this year with the ABL.
Leverage with 2.5 times at the end of the second quarter.
That's flat to where we were at the end of the second quarter of 2020, and an increase of 20 basis points from the end of the first quarter this year, mainly due to the acquisition of General Finance in May.
We finished the quarter with over $2.8 billion in total liquidity.
That's made up of ABL capacity of just under $2.4 billion and availability on our AR facility of $106 million.
We also had $336 million in cash.
We've raised our full year guidance ranges at the midpoint by $350 million in total revenue and $100 million in adjusted EBITDA, as we now expect stronger double-digit growth for the core business in the back half of the year.
That increase for acquisitions reflects $250 million in total revenue and $60 million in adjusted EBITDA, which includes $15 million of expected full year one-time costs.
To that end, we raised our growth capex guidance by $300 million, a good portion of which reflects fleet we are purchasing from Acme Lift.
It remains a robust $1.7 billion at the midpoint and we'll continue to earmark our free cash flow this year toward debt reduction to enhance the firepower we have to grow our business.

Summary:
I'll shift to adjusted EPS, which was $4.66 for the second quarter, including a $0.13 drag from one-time costs.