Ball-bearing blocks run rope with less friction so lines ease and trim smoothly under working loads; plain-bearing blocks tolerate far higher static loads at lower cost and lower maintenance. Choose ball-bearing for anything you actively trim (mainsheet, jib sheet, control lines). Choose plain-bearing for anything that sits under high, near-static load (halyard turning blocks, high-load deflection points, cruising hardware).
The bearing is the mechanical heart of a sailboat block — it sits between the sheave and the axle and decides two things that matter more than the block's outward shape: how much friction the line sees when it moves, and how much load the block can sit under without deforming. Ball-bearing blocks put a ring of hard, low-friction spheres (typically Torlon) between the sheave and the axle. Plain-bearing blocks run the sheave directly on a smooth bushing or a hardened pin. Both are current, live technology — they solve different problems, and most well-outfitted boats end up with a mix of both.
Ball-bearing vs plain-bearing blocks at a glance
| Block (SKU) | Bearing type | Sheave | Working load | Breaking load | Best for |
|---|---|---|---|---|---|
| Harken Carbo 29mm Double (HAR342) | Ball bearing (Torlon) | 29 mm | 299 kg / 670 lb | 1,625 kg / 3,583 lb | Dinghy & small-boat trim lines |
| Selden 20 BB Double (SEL40210103R) | Ball bearing | 20 mm | 300 kg | 600 kg | Small control-line purchases |
| Ronstan S40 BB Orbit Double (RONRF48200) | Ball bearing | 40 mm | 600 kg / 1,323 lb | 1,200 kg / 2,646 lb | Mainsheet & jib-sheet purchases up to ~35 ft |
| Selden 100 Plain-Bearing Single (SEL41000101R) | Plain (bushing) | 100 mm | 4,000 kg | 8,000 kg | Halyard turning blocks, cruising deflection |
| Lewmar 105mm High-Load Single (LEW29941101BK) | High-load rolling | 105 mm | 3,750 kg / 8,268 lb | Not published | Big-boat halyard & primary sheet turning |
Working- and breaking-load figures are the manufacturer's published values pulled from the live MAURIPRO product database. "High-load rolling" refers to the compact Torlon-bearing ring Lewmar fits to its 105 mm high-load line — it sits between a pure ball-bearing block and a pure plain-bearing block in behaviour and price.
How does a ball-bearing block actually reduce friction?
A ball-bearing block replaces sliding contact with rolling contact. The sheave rides on a caged ring of hard spheres — Harken uses Torlon on its Carbo line, Ronstan uses Torlon in its Orbit BB range, Selden's ball-bearing sheaves use precision polymer balls — and the whole assembly turns with the line rather than dragging against the axle. The measurable payoff is that the block spins freely under load, which is exactly what a sheet block, guy block, or fine-tune control block needs: you can ease under pressure, sheet in through a purchase, and re-trim without the block "locking" and forcing the crew to yank slack out by hand.
The physical price is capacity. Ball bearings concentrate the load on tiny contact patches, so ball-bearing blocks are engineered for a defined working range — the Harken Carbo 29 mm double is rated for 299 kg working / 1,625 kg breaking, and the Ronstan S40 BB Orbit double for 600 kg working / 1,200 kg breaking. Push a ball-bearing block past its rated working load repeatedly and the sheave slows, the balls deform, and the friction advantage disappears.
When is a plain-bearing block the right call?
A plain-bearing block runs the sheave directly on a machined bushing or a hardened pin. There are no balls, no cage, and no delicate contact patches — the load is spread evenly across the full width of the bushing. That geometry is why plain-bearing blocks scale up so cleanly: the Selden 100 plain-bearing single is rated for a 4,000 kg safe working load and an 8,000 kg breaking load in a package that weighs about 1 kg. You physically cannot get that load rating out of a similarly sized ball-bearing block.
The trade-off is friction. Plain-bearing blocks spin under sliding contact, so they need real force to move — which is fine if the block sits under load and only turns occasionally (a masthead halyard block, a deflection at the base of the mast, a cruising boat's spinnaker turning block). It is a bad choice for a mainsheet-fine-tune purchase, where the crew is easing and trimming under pressure every few seconds.
How does the bearing choice affect longevity?
Plain-bearing blocks usually outlive ball-bearing blocks in salt water. There are no small parts to lose, no fine tolerances for salt crystals to jam, and rinsing the block clears the bushing. A plain-bearing masthead sheave installed by a first owner is often still on the boat 15–20 years later, running the same halyard.
Ball-bearing blocks demand more discipline. UV, dried salt, and grit shorten Torlon-bearing life, so racing sailors flush their blocks with fresh water after every day on the water and replace bearings on a schedule. A hard-run mainsheet block on a performance boat sees the same abuse in a season that a plain-bearing halyard block sees in a decade. In practical terms: if you are outfitting a cruising boat you plan to maintain lightly, weight the running rigging toward plain bearings; if you are outfitting a race boat and will maintain the hardware seriously, ball bearings are worth the extra care.
What about high-load "rolling" blocks — where do they fit?
Manufacturers now offer a middle category for big boats: high-load blocks with a compact rolling-element bearing (Lewmar's 105 mm and 130 mm High-Load line, Harken's Black Magic, Ronstan's High-Load Orbit). These blocks keep enough of the ball-bearing's low-friction spin to trim under load, but they raise the load ceiling toward plain-bearing territory. The Lewmar 105 mm high-load single is rated for a 3,750 kg working load — an order of magnitude above the Harken Carbo 29 mm — while still spinning free enough for a primary mainsheet block on a 45–55 ft cruiser-racer.
The price envelope moves with the capability: a small Carbo double is under $60, a mid-range Orbit double lands around $150, a Lewmar 105 mm high-load block runs into the several-hundred-dollar range, and a large plain-bearing halyard block sits in the low-to-mid hundreds. For most private owners, the honest choice is not a single bearing type but a coherent mix.
Which should I choose?
- Mainsheet, jib sheet, vang purchase, kicker, control lines: ball-bearing. You trim these under load; friction is the enemy.
- Masthead halyard blocks, deck-organiser turning blocks, cruising boat's genoa lead: plain-bearing. They sit under load and rarely spin fast; capacity and salt tolerance win.
- Primary mainsheet turning block on a 40 ft+ cruiser-racer, big-boat spinnaker sheet block: high-load rolling. Sizes up without giving away the trim-under-load feel.
- Dinghy or one-design: ball-bearing, sized to the class-legal or class-typical maximum load — the friction savings show up immediately at low sheet forces.
A short but useful rule: if a human hand is hauling on the line and adjusting position every few seconds, use a ball-bearing block. If the line is set-and-forget under thousands of kilos, use a plain-bearing block. If both are true (big boat, actively trimmed), look at the high-load rolling category.
Frequently asked questions
Are ball-bearing blocks stronger than plain-bearing blocks?
No — the opposite is usually true. Plain-bearing blocks carry higher working and breaking loads per unit size and weight because the sheave rides on a full-width bushing rather than concentrated on small balls. Ball-bearing blocks win on friction, not on raw capacity.
Can I use a plain-bearing block for a mainsheet?
You can — the block will not fail — but the crew will feel it. Plain-bearing blocks need real force to spin, so easing under load is jerky and re-trimming is heavier than it should be. On anything above a small keelboat, a mainsheet system almost always uses ball-bearing (or high-load rolling) sheaves for a reason.
Do ball-bearing blocks need maintenance?
Yes. Rinse them with fresh water after every sail, avoid solvents that attack the polymer bearings, and inspect the sheave for flat-spotting under heavy use. Torlon bearings themselves are a wear part on hard-run racing blocks; most manufacturers publish replacement schedules.
Torlon vs Delrin balls — does the material matter?
Yes, at high load. Torlon (a high-performance polyamide-imide) tolerates far higher contact pressures than Delrin acetal and stays dimensionally stable at higher temperatures. Racing and performance blocks (Harken Carbo, Ronstan Orbit BB) use Torlon. Some low-load blocks use Delrin because the load never approaches the material limit — and Delrin is cheaper.
Is a "roller-bearing" block the same as a ball-bearing block?
Not exactly. Roller-bearing blocks use cylindrical rollers instead of spheres. They spread the load along a line contact rather than a point contact, so they typically carry more load than a same-size ball-bearing block while keeping most of the low-friction spin. Some manufacturers market their high-load blocks as "rolling" or "roller" bearing lines for exactly this reason.
Can I mix bearing types in the same purchase system?
Yes and it is common practice. A typical mainsheet system uses ball-bearing sheaves at the boom-end and traveller car (where the trimmer works the line) and can safely use a plain-bearing turning block at the base of the mast (where the line is deflected and does not need to spin freely). Match each block to what its position actually asks of it.
Shop the collection
Every block above is a live product in the MAURIPRO catalog. Browse the full range — ball-bearing, plain-bearing, and high-load rolling — at Shop all Sailboat Blocks → and pair with our Choosing Sailboat Blocks buyer's guide and Single vs Double vs Triple Blocks to build out the full purchase system.