Silicone Reducer Hose: How to Specify Both End Sizes

To select a silicone reducer hose, confirm the size at each end and the overall length. This guide explains how to check both end sizes, read the product specifications and prepare the information needed for an inquiry.

A reducer hose connects two lines of different diameters — a charge-air pipe to an intercooler outlet, for example, or two sections of a cooling line. Because the two ends are different sizes, “one diameter” is never enough. Specifying only one end size can lead to an incorrect selection. This guide walks through the four points that define a correct inquiry:

Pipe OD vs. hose ID — which one to measure
Both end IDs (ID1 & ID2)
Total length: transition section and straight clamping sections
The information to include in your inquiry

1. Check the Pipe OD and Hose ID

Measure the actual outside diameter (OD) of each mating pipe end with calipers. Do not rely only on the nominal pipe size. Check each measured pipe OD against the corresponding hose inside diameter (ID) and the fit requirements in the product drawing. Equal dimensions, or a larger hose ID, do not by themselves confirm a suitable fit.

2. Give both end IDs — ID1 and ID2

A straight silicone reducer hose has a different ID at each end. In this guide, ID1 refers to the smaller end and ID2 to the larger end.

In the HSTR part number, the two figures are the two end IDs, smaller end first. For HSTR276/374, the listed hose IDs are 2.76 inch (70 mm) at the smaller end and 3.74 inch (95 mm) at the larger end. The wall thickness is 0.18 inch / 4.50 mm, with a tolerance of ±0.02 inch / ±0.5 mm.

Part No.	ID1 (inch / mm)	ID2 (inch / mm)	OD1 (inch / mm)	OD2 (inch / mm)	Ply	Wall thickness
HSTR110/138	1.10 / 28	1.38 / 35	1.46 / 37	1.73 / 44	3	0.18 inch / 4.50 mm
HSTR150/200	1.50 / 38	2.00 / 51	1.85 / 47	2.36 / 60	3	0.18 inch / 4.50 mm
HSTR177/248	1.77 / 45	2.48 / 63	2.13 / 54	2.83 / 72	3	0.18 inch / 4.50 mm
HSTR200/300	2.00 / 51	3.00 / 76	2.36 / 60	3.35 / 85	3	0.18 inch / 4.50 mm
HSTR224/300	2.24 / 57	3.00 / 76	2.60 / 66	3.35 / 85	3	0.18 inch / 4.50 mm
HSTR248/350	2.48 / 63	3.50 / 89	2.83 / 72	3.86 / 98	3	0.18 inch / 4.50 mm
HSTR276/374	2.76 / 70	3.74 / 95	3.11 / 79	4.09 / 104	3	0.18 inch / 4.50 mm
HSTR300/400	3.00 / 76	4.00 / 102	3.35 / 85	4.37 / 111	3	0.18 inch / 4.50 mm
HSTR350/450	3.50 / 89	4.50 / 114	3.86 / 98	4.84 / 123	3	0.18 inch / 4.50 mm
HSTR400/500	4.00 / 102	5.00 / 127	4.37 / 111	5.35 / 136	3	0.18 inch / 4.50 mm
HSTR400/600	4.00 / 102	6.00 / 152	4.37 / 111	6.34 / 161	3	0.18 inch / 4.50 mm

All dimensions are shown as inch / mm. ID1 and ID2 are the hose inside diameters; OD1 and OD2 are the hose outside diameters. These OD values are not the mating-pipe ODs.

3. Total length: transition + two straight clamping sections

A reducer hose is not just two diameters — its length is made of three parts:

Straight section at one end (S1) — the straight end section where the first hose clamp grips.
Transition (taper) section (T) — the cone that steps between the two diameters.
Straight section at the other end (S2) — the seat for the second clamp.

Clamps seat on straight sections, never on the taper. If the transition lands under a clamp, the clamp cannot seal evenly and the hose may deform. When you specify length, state the total (L) with its unit; if your drawing requires specific straight-section lengths, list them as well. For installation requirements, refer to the product documentation.

4. Information to Include in Your Inquiry

Example Inquiry for HSTR276/374

Inquiry Item	Example / Information to Provide
Part number	HSTR276/374
ID1 — smaller end	2.76 inch / 70 mm
ID2 — larger end	3.74 inch / 95 mm
Wall thickness	0.18 inch / 4.50 mm (±0.5 mm)
Ply	3
Total length L	to be specified — state the unit (inch or mm)
Straight sections S1 / S2	per drawing
Quantity	e.g. 20 pieces — state the unit
Application	e.g. charge-air line or cooling line
Fluid or gas	e.g. air or coolant
Operating temperature	if known — otherwise confirm during the inquiry
Working pressure	if known — otherwise confirm during the inquiry

Send us both end sizes, the required overall length with units, and quantity to start an inquiry. If you are unsure of the hose IDs, provide the measured pipe ODs and a connection photo. Please also share the application, fluid or gas, operating temperature and working pressure if available, so we can review a suitable option.

Contact: steven@hunthose.com
Phone: +8613480490693
Website: www.hunthose.com

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