Parts of a Compound Bow, From Riser to D-Loop
A compound bow has about ten parts that matter: riser, limbs, cams, modules, cables, cable guard, string, peep, D-loop, and draw stops. Here's what each one does — and which ones deserve your money.
By the Archery Care Editorial Team
Ten parts, more or less, make up a compound bow: the riser you grip, the limbs that store energy, the cams that multiply it, plus cables, a cable guard, the string, and the small stuff — peep sight, D-loop, draw stops. Learn what each one does and pro shop conversations get cheaper fast.
Here's the full tour, top to bottom.
The riser
The riser is the rigid center section — the part you actually hold. Your sight, arrow rest, stabilizer, and quiver all bolt to it. Most risers are machined from aluminum. Carbon versions cut weight and don't pull the heat out of your hand in a November treestand, which is a big part of why a Hoyt Carbon RX-10 costs what it does.
Stiffness here matters more than the brand. A riser that flexes under load bleeds accuracy you'll never buy back with accessories.
Limbs
Think of the limbs as the bow's springs — fiberglass-composite blades bolted to each end of the riser that bend as you draw. All the energy that launches your arrow lives in them, not the string. You'll see solid limbs (one piece) and split limbs (two blades with a gap between them). Most modern hunting bows run near-parallel limb geometry, which sends the limbs in opposite directions at the shot and cancels most of the kick.
Cams and modules
Cams do the trick that defines the category. These machined, egg-shaped wheels at the limb tips change leverage through the draw cycle, so the bow gets harder to pull and then suddenly easier — that drop is let-off. Modern designs advertise 80 to 90 percent, meaning a 70-pound bow holds somewhere between 7 and 14 pounds at full draw. The Mathews ARC 34 offers 80 or 85 percent on its SWX-2 cam.
Three layouts dominate:
- Single cam — one power cam on the bottom limb, a round idler wheel on top. Forgiving to tune, a touch slower.
- Hybrid — a control cam and a power cam working together off shared cables.
- Binary — twin cams slaved to each other. Fast, crisp draw, and what most flagships run.
Modules set your draw length
Bolted onto the cam itself, modules are the small plates that set your draw length — and on some bows, your peak weight too. The ARC 34's mods cover 26.5 to 32 inches of draw and 55 to 80 pounds without a bow press, which is why that bow runs $1,569 instead of less. Get measured before you buy anything. A draw length calculator and your wingspan will get you close; a pro shop will get you exact.
Cables and the cable guard
Look past the string and you'll see two thick cables running between the cams. They keep the system synchronized so both cams roll over together — when they don't, your bow is out of time and your arrows know it before you do.
The cable guard, a rod or roller bracket jutting sideways from the riser, pulls those cables out of the arrow's flight path. Older guards use a Teflon slide; most current bows use rollers. Torn fletchings? Check here first.
The bowstring
Strings take the abuse. They're woven from high-modulus polyethylene fibers — Dyneema and its cousins — and they creep and fray quietly over thousands of shots. Wax yours when it looks fuzzy. Plan on a replacement roughly every three years, sooner if you shoot a lot, because a stretched string shifts your draw length and peep rotation without announcing itself.
Peep sight and D-loop
Two small string-mounted pieces finish the aiming system.
The peep sight is a little ring served between the strands of the string. You look through it to center your sight housing, the way a rifle shooter uses a rear aperture. Set its height for the distance you shoot most often — not your maximum.
The D-loop is a short cord tied around the string at the nocking point. Your release aid clips to the loop instead of the string, which protects the serving and keeps nock travel straight. The material costs pennies. Replace it the moment it looks chewed.
Draw stops and the back wall
At full draw, something has to tell your muscles to quit pulling. That's the draw stop, and it creates what archers call the back wall. Cable stops press against a cable and feel slightly spongy. Limb stops hit the limb directly and feel like concrete. Target shooters mostly want concrete; some hunters prefer a hint of give for awkward treestand angles. Plenty of current cams let you run either.
What the parts tell you about price
One warning before you shop on specs. Advertised speeds come from lab conditions — the ATA standard fires a 350-grain arrow from a 70-pound bow at a 30-inch draw, and the older IBO test allows 80 pounds and a 400-grain arrow. A real hunting setup typically lands around 270 to 285 fps regardless of the sticker.
Across the compounds we've scored, IBO ratings span just 338 to 357 fps while prices run $1,300 to $2,149. That's 19 fps across an $849 gap.
So buy for riser stiffness, cam feel, and the back wall. The speed number is the least interesting part on the bow.