All of the major indices either closed at record highs or broke intraday records last week, and much of the bullishness centered around small-cap stocks. The Russell 2000 small-cap index, for instance, gained 6% in September while the S&P 500 wafted up less than 2%. Small caps are where the action is.

Part of the reason is that smaller firms pay higher taxes (roughly 33%, vs. 27% for large-cap companies), meaning small-cap stocks benefit the most from tax reform.

But small caps aren’t without risk. Some critics see small firms being hurt by earnings season as growth slows and price-earnings ratios are perched atop highs not seen in 16 years. That’s why I’m specifically looking at undervalued small caps growing at breakneck speeds.

You may not recognize some of these names, and they may not be crawling with analysts, but these are the top small-cap stocks with highest upside potential in the market right now:

Small-Cap Stocks: Ichor (ICHR) Is High Growth, No Nonsense

Year-to-date gain: 146%
P/E ratio: 9.5
Long-term earnings growth: 29.3%

Ichor Holdings Ltd (NASDAQ:ICHR) is a semiconductor play. It may not be as recognizable as Advanced Micro Devices, Inc. (NASDAQ:AMD) or as sexy as Nvidia Corporation (NASDAQ:NVDA), but it’s got the wind from several trends at its back.

Aside from semiconductors, Ichor has businesses in OLED, alternative energy, data storage and flat panel display. OLED, for instance, is rapidly growing, as Apple Inc. (NASDAQ:AAPL) recently transitioned to the material for iPhone X after years of Samsung Electronics using it for its Galaxy lineup. Ichor manufactures and designs the machines that create OLED screens, which is a market expected to hit nearly $44 billion by 2020 as more applications become available. Data storage, to cherry pick another example, will be a $145 billion market by 2022.

But Ichor’s “end-market drivers” (PDF) are in cloud computing, mobility, connectivity and Big Data. Demand in these areas has pushed Ichor’s annual revenue to grow at a rate of 28%, from $249 million in 2014 to $406 million last year.

Over the next five years, ICHR is slated to grow earnings at a pace of 29.25%, and for that, you only pay a measly nine times forward earnings!

Small-Cap Stocks: Beasley Broadcast (BBGI) Makes Waves

YTD gain: 90%
P/E ratio: 5
Earnings growth: 29%

If this is your first time hearing of Beasley Broadcast Group Inc (NASDAQ:BBGI), rest assured knowing it won’t be your last. BBGI reaches more than 19 million listeners through news and music across 63 stations in 15 U.S. markets.

Its logo also looks suspiciously like Apple’s Beats, but that’s a conversation to have with a graphic designer.

You might ask yourself why anyone would want to invest in the not-so-burgeoning area of radio, and the answer is market opportunity and diversification. Nearly half of Beasley’s stations are in prime markets like Miami, Las Vegas, Atlanta and Boston. Its stations run the gamut, from oldies and pop music to talk radio and sports.

The question of whether it makes money is moot — BBGI is growing earnings at a 29% clip for the next five years. Revenue, too, is up 120% year-over-year according to BBGI’s second-quarter report. Not bad for a radio company birthed in the ’60s. When you consider its trailing P/E ratio of 5, it’s a steal.

Oh, and BBGI stock throws off a dividend yield of 1.5%, which is far more than you’d get from Jeff Bezos & Co.

Small-Cap Stocks: Callaway Golf (ELY) Is a Hole in One

YTD gain: 33%
P/E ratio: 8
Earnings growth: 30.9%

Callaway Golf Co (NYSE:ELY) has been in the business of manufacturing and selling golf clubs, balls and accessories for 30-plus years, which is just about as exciting as it sounds. But sexy is overrated, and ELY stock is a firebrand in disguise. Since 1992, Callaway has gained 260% in the markets, which isn’t bad considering that it used to trade over 60% higher than it does today.

It may never reach those lofty heights of the late ’90s again, but ELY stock is an opportunity right now.

The company has pulled itself out of an earnings tailspin — from a per-share earnings loss of $1.96 in 2012 to a gain of $2.02 in 2016 — and is making savvy business decisions like signing up-and-coming stars like Maverick McNealy.

Speaking of star power, Callaway is heavily represented at the Presidents Cup. It’s also making the right M&A moves, buying out the TravisMathew apparel brand for $125.5 million.

It’s doing something right, after all, as its Q2 report reveals double-digit sales growth and forward guidance.

While its trailing P/E is only 8, its forward P/E is a much-higher 29. Still, that’s a perfectly acceptable multiple for a company growing earnings at a 31% clip for the next five years.

Small-Cap Stocks: Hoegh LNG (HMLP) Is a Portfolio Fill-Up

YTD gain: -0.5%
P/E ratio: 0.3
Earnings growth: 30.2%

Hoegh LNG Partners LP (NYSE:HMLP), as you could glean from its ticker, is a master limited partnership (MLP) that deals in liquid natural gas (LNG) services. Its stock is in the red this year by virtue of being in energy, but now could be the time to buy the dip)!

I’m not alone in that opinion either. Of the nine analysts covering HMLP stock, nine of them encourage buying it. In its Q2 report, Hoegh posted revenue growth of 54% and earnings growth of 200%! Analysts expect 53% revenue growth for the full year — from $91.1 million to $139.4 million — and earnings growth for the current year is also in the double-digits — 23%.

That’s a lot of growth, and it’s even more mouth-watering when you consider the forward P/E ratio is 11. Even better, remember how I mentioned how Hoegh is an MLP? That means that it must pay 90% of its profits out to shareholders in the form of a distribution.

So for your “troubles” of owning HMLP stock, you get a distribution yield of 9.1%.

Small-Cap Stocks: MannKind (MNKD) Gets a Shot in the Arm

YTD gain: 61%
P/E ratio: 3.8
Earnings growth: 26.8%

It’s been a while since I last wrote about MannKind Corporation (NASDAQ:MNKD) — more than two years to be exact. Since that article was published, MNKD stock has given back 83% (which kind of makes me want to turn the comments back on so I can rub my prescience in the trolls’ faces). But now, MNKD stock looks like a winner.

That doesn’t mean I don’t have a bone to pick with MannKind — I do. That is, MNKD stock is just so darn volatile! I dreamt this article up when MNKD had an 11% gain in the can for the year, before investors bid it up 40% in one day on an FDA label change. On the flip side, at least it’s not merely 100% speculation. The FDA label change will likely assist in selling doctors and prescribers on Afrezza and even toward increasing patient’s attitudes toward the drug.

Right now, Afrezza cartridges total 87,000 across all of its prescriptions on a weekly basis and the market of diabetics who aren’t achieving desired results of blood glucose levels with traditional insulins is quite large.

For the next five years, MNKD is expected to grow earnings at 26.8% per year, but that number could be much higher if Afrezza takes off in a meaningful way.

John Kilhefner is the deputy managing editor of InvestorPlace.com. He does not hold a position in any of the aforementioned securities. Follow him on Twitter at @jkilhefner.