Adapters · 5 combinations
ROCKLER Dust Right stacking port adapter set, 3 piece
Five connections from three parts, color-coded, in glass-reinforced polypropylene — and they nest when they are not in use.
Every figure below names its source. Each one is a manufacturer
specification read off the listing itself. The judgments are ours.
Three parts, five steps
Each adapter is a step with a male end and a female end, so they chain: the
output of one feeds the input of the next.
Three used singly and in pairs reach five reductions, from four inches down to
an inch and a quarter.
The listing publishes the count. It does not publish the five sizes, which is
the gap — a buyer knows there are five and not which five.
The POWERTEC fittings on this shelf publish actual diameters and no
combinations. This publishes combinations and no diameters.
Black, grey, blue
Large, medium, small — and the only color coding on either half of this shelf.
A workshop accumulates adapters. They are all black, all round, all nearly the
same size, and the right one is found by trying three.
Color is the cheapest possible fix, and the fact that they nest means the set
stays together, which is the other half of the same problem.
Glass-filled polypropylene
The right plastic for a part that lives in a drawer.
Polypropylene flexes rather than snapping, and glass fiber adds the stiffness
plain PP lacks — so the part survives a concrete floor and a hose twisted off
cold.
ABS, which four fittings on this shelf are made of, is stiffer and more abrasion
resistant inside a duct, and it cracks.
For a drawer part, this. For a part cemented into a wall run, that.
Why nominal is not a measurement
A four-inch fitting is not four inches anywhere on it.
The POWERTEC listings on this shelf publish the actual figures: a four-inch
nominal end measures 3-31/32 in across the outside and 3-39/64 in across the
inside — 100.8 mm (3.97 in) and 91.7 mm (3.61 in). The difference between those two is the wall, and
the difference between one maker’s outside and another’s inside is the leak.
That is what the shelf’s own intro means by the adaptors that never quite fit.
Nominal sizing is a naming convention; the join is decided by the sixty-fourths.
And no diameters at all
Four inches, three inches, an inch and a quarter — nominal, every one.
Which on the shelf whose intro names the adaptors that never quite fit is the
one thing a fitting page should not leave out.
Availability
Read on the day this page was built: $21 at the American Amazon shop.
Read from Keepa on the day this page was last revised; stock and price both move without notice.
Prices quoted in this text were read on 2026-10-07. The live price is at the top of the page.
