Do Aero lowers fit YHM uppers?
Aero lower + YHM upper: yes, they fit
Yes. Aero Precision AR-15 lowers fit Yankee Hill Machine (YHM) AR-15 uppers. Both are AR-15 size receivers. A real mil-spec keeps AR-15 receivers from different makers close, though not exact, and fit problems show up most when the upper and lower come from different makers. We checked them with the rules the AR builder runs.
Fit comes from the same rules the AR builder runs on every part you add. Build data only ranks the setups; it never decides fit. Checked October 31, 2026.
Our take
Most built setup: the Aero Stripped M4E1 lower with the YHM A3 upper.
About 1 in 45 Aero lowers in our builds carries a YHM upper.
Aero makes forged AR receivers, mainly the M4E1 line, with a billet look that still takes standard mil-spec parts. They also make complete uppers, charging handles and rifles.
Founded 1994, Tacoma, Washington, Made in USA
Yankee Hill Machine (YHM) makes suppressors, handguards, muzzle devices and gas blocks at fair prices, from a family shop in western Massachusetts.
Founded 1951, Easthampton, Massachusetts, Made in USA
Aero lowers and YHM uppers by platform
Each row is checked on the most built part of that platform from each brand.
| Platform | Fit |
|---|---|
| AR-15 | Yes, they fit |
AR-15: yes, they fit
Both are AR-15 size receivers.
Checked on this Aero lower
Aero Precision Stripped M4E1 Lower Receiver$154.99, out of stockand this YHM upper
Yankee Hill Machine A3 Upper Receiver$121.75Most built Aero lowers and YHM uppers setups
Ranked by how often builders pick the exact pair. Only pairs our rules pass are listed.
#1Yes, they fit23% of these buildsCheck fit
#2Yes, they fit9% of these buildsCheck fit
#3Yes, they fit7% of these buildsCheck fit
#4Yes, they fit7% of these buildsCheck fit
#5Yes, they fit7% of these buildsCheck fit
#6Yes, they fit4% of these buildsCheck fit
#7Yes, they fit4% of these buildsCheck fit
#8Yes, they fit3% of these buildsCheck fit
What Aero and YHM say
Aero Precision: The M4E1 upper is forged 7075-T6 with a billet style look, and it still takes a standard barrel nut and mil-spec parts.
Aero Precision: The rear takedown pin detent hole on Aero's Gen 2 AR15 lower is threaded for a 4-40 set screw.
Aero Precision: Aero's Gen 2 AR15 lower is machined to mil-spec dimensions, works with standard AR15 parts and magazines, and has a nylon tipped tension screw for a tight fit with any standard AR15 upper.
YHM: YHM sells complete and stripped uppers and lowers, plus its own carbines.
YHM: The lower in YHM's billet receiver set fits all standard parts except a trigger guard, has a built in tension screw and takes every generation of PMAG.
YHM: YHM's A3 upper has M4 style feed ramps and T marks, and accepts standard upper parts and mil-spec lower receivers.
YHM: YHM's stripped A3 upper comes without the forward assist and dust cover, while the A3 upper assembly includes both.
Fit is judged from the specs retailers list, which can be missing or wrong. Confirm with the manufacturer before you buy, and have a qualified gunsmith check any build before you fire it.
Other uppers builders put on Aero lowers
- Aero lowers + Aero uppersMost picked
- Aero lowers + BCM uppersSecond most picked
- Aero lowers + Geissele uppersThird most picked
- Aero lowers + Wilson Combat uppersFourth most picked
- Aero lowers + PSA uppersFifth most picked
- Aero lowers + Daniel Defense uppersSixth most picked
- Aero lowers + Radical uppersSeventh most picked
- Aero lowers + TacFire uppersNinth most picked
Other lowers under YHM uppers
- YHM lowers + YHM uppersThird most picked
- PSA lowers + YHM uppersFourth most picked
Aero lowers and YHM uppers: questions builders ask
Will a YHM upper fit an Aero lower?
Yes. Aero AR-15 lowers fit YHM AR-15 uppers. Both are AR-15 size receivers.
Do I need a matched upper and lower?
A real mil-spec keeps AR-15 receivers from different makers close, though not exact, and fit problems show up most when the upper and lower come from different makers.
Why might a YHM upper feel loose or tight on an Aero lower?
Some play between an AR-15 upper and lower is common, but it can get excessive when the two come from different makers, and a tension screw or an Accu-Wedge takes it up.