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Sta-Lok stemballs in 316 stainless steel: swage (5/32 to 3/4 in wire), swageless (7/32 to 3/8 in), left-hand threaded for turnbuckles, and stemball cups. Click here to read more.

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Sta-Lok Stemballs: Swage, Swageless, Threaded and Cups for Standing Rigging

A stemball is the ball-shaped terminal on the end of a rigging wire that seats in a cup or socket at the mast fitting or spreader bracket. Every stemball in this collection is Sta-Lok, made from 316 stainless steel. The choice comes down to how the wire is terminated (swage, swageless or a threaded stud for a turnbuckle), the wire diameter and whether the head fits your bracket.

Stemball Types in This Collection
  • Swage stemballs: 18 listings for wire from 5/32 in (the 042-04) up to 3/4 in (the 042-19), for example the 10 mm and the 1/2 in. They are made for rotary and fixed-die swaging machines and work with 1x19, 7-strand and compacted strand (IWRC) wire rope, metric and inch.
  • Down-size head swage stemballs: the 3/16 in and 9/32 in with a smaller head, for brackets that take a smaller ball. The 12 mm 042-12E is swaged with E dies.
  • Swageless stemballs: 7 listings from 7/32 in (the 146-55) to 3/8 in (the 146-10), including 6 mm and 10 mm. Sta-Lok describes them as the reusable alternative to swage: basic hand tools, no pre-measurement, for right-hand and left-hand lay wire. They are packed for 1x19 wire, with different wedges for 7-strand and compacted wire, and Sta-Lok recommends threadlock on the two-part assembly. Example: the 6 mm swageless.
  • Threaded stemballs (left hand): 11 listings from 1/4 in to 1 1/8 in thread, including a small-head 5/16 in, for Sta-Lok turnbuckles. They are left-hand thread only and suit all Sta-Lok turnbuckles. Example: the 1/2 in.
  • Stemball cups (stainless steel): the 3/16 in (5.0 mm) and 5/32 in (3.97 mm), which bring the head up to fit a mast or spreader bracket. One or two cups may be needed.
How to Choose a Stemball
  • Wire diameter first: the stemball must match the wire. Sizes are listed in both inch and mm wire diameters, so read the title against your wire, not against the bracket.
  • Swage or swageless: swage needs a swaging machine and a pre-measured wire. Swageless fits with hand tools and can be reused, so it suits repairs afloat. In this collection swageless stops at 3/8 in wire, where swage goes up to 3/4 in.
  • Head size and cups: the head has to seat in your mast fitting. Sta-Lok designs its swage stemballs to suit most backing plates, and says a stemball cup may be required. If your original has a smaller head, look at the down-size versions.
  • Hole depth: the swage listings give a minimum hole depth of 10 times the wire diameter in the fitting.
  • Threaded: choose by thread size, and note that it is left-hand only.
Who It's For

Riggers and owners replacing or re-terminating shrouds, stays and backstays, and boats with spreader brackets or mast fittings that take a stemball. Pair a threaded stemball with a Sta-Lok turnbuckle, or browse the Sta-Lok swageless eye terminals for other wire ends.

Frequently Asked Questions

What is a stemball?
A ball-shaped terminal fitted to the end of a standing rigging wire. The ball seats in a cup or socket at the mast fitting or spreader bracket.

Can I fit a stemball without a swaging machine?
Yes, with the swageless type: Sta-Lok says basic hand tools are enough and the terminal can be reused. The swageless range covers wire from 7/32 in to 3/8 in.

What wire do Sta-Lok swage stemballs fit?
1x19, 7-strand and compacted strand (IWRC) wire rope, in metric and inch sizes. Match the stemball to the wire diameter in the title.

Do I need a stemball cup?
Maybe. Sta-Lok says one or two stemball cups may be required to bring the head up to the size your mast or spreader bracket needs, and lists 3/16 in and 5/32 in cups. Check the fit against your bracket before ordering.

What is a threaded stemball for?
It screws into a turnbuckle. The thread is left-hand only and the listing says it suits all Sta-Lok turnbuckles. See our guide to Sta-Lok Supajust turnbuckles.