Rigid Compression Fittings Buyer's Guide: Threadless Couplings and Connectors for RMC and IMC
Sep 25, 2026
Threading rigid conduit on a jobsite takes a pipe vise, a threader, cutting oil and time. Threadless compression fittings skip all of that. You cut the conduit square, slide on the fitting, and tighten the compression nut with a wrench. This guide covers what these fittings are, where they are allowed, how to size them, and how our RTC and RT series cross to the part numbers your supply house already knows.
What a rigid compression fitting is
A rigid compression fitting has a steel body with a tapered seat, a split compression ring, and a compression nut. Tightening the nut drives the ring against the conduit wall, which grips it mechanically and gives a continuous electrical path for equipment grounding. The fitting is sized for the outside diameter of rigid metal conduit (RMC) and intermediate metal conduit (IMC), which share the same OD in each trade size. That is why one fitting covers both, and why these fittings will not seal on EMT, which has a smaller OD.
- Coupling joins two lengths of conduit end to end. Our part numbers are RTC-50 through RTC-200.
- Connector terminates conduit into a box, enclosure or panel through a knockout, secured with a locknut. Our part numbers are the RT series, for example RT-150.
When to use threadless instead of threaded
- Field cuts and repairs. When a run is cut to length on site and there is no threader on the truck.
- Tight spaces. Where you cannot rotate a length of conduit to thread it into a coupling.
- Retrofit and tie ins. Splicing into existing rigid runs without disturbing the rest of the raceway.
- Speed. A wrench tightened fitting installs in a fraction of the time of cutting threads.
Threadless fittings on rigid and IMC are permitted under NEC 344.42(B) and 342.42(B) when listed for the purpose. Always confirm the listing marked on the fitting matches your application, and check with the AHJ where local amendments apply.
Ratings to look for
- UL 514B. The standard for conduit, tubing and cable fittings. Our RTC and RT series carry the UL 514B listing.
- Concrete tight. Our RT series connectors are marked concrete tight. Check the product page for the specific size you need.
- Finish. Zinc plated steel for corrosion resistance indoors and in protected outdoor locations. For wet locations, direct burial or corrosive environments, specify a fitting listed for that use.
Sizing: trade size and conduit OD
Rigid and IMC share these outside diameters. Match the fitting to the trade size stamped on the conduit.
| Trade size | RMC / IMC OD | CT coupling | CT connector |
|---|---|---|---|
| 1/2" | 0.840" | RTC-50 | RT-50 |
| 3/4" | 1.050" | RTC-75 | RT-75 |
| 1" | 1.315" | RTC-100 | RT-100 |
| 1-1/4" | 1.660" | RTC-125 | RT-125 |
| 1-1/2" | 1.900" | RTC-150 | RT-150 |
| 2" | 2.375" | RTC-200 | RT-200 |
Cross reference
Couplings and connectors are separate part families at both manufacturers. Bridgeport offers each in a standard malleable iron version and an RT (raintight) steel version; the RT suffix is the wet location listing.
Couplings
| Trade size | CT | RACO | Bridgeport | Bridgeport raintight |
|---|---|---|---|---|
| 1/2" | RTC-50 | 1822 | 3100 | 3100-RT |
| 3/4" | RTC-75 | 1823 | 3101 | 3101-RT |
| 1" | RTC-100 | 1824 | 3102 | 3102-RT |
| 1-1/4" | RTC-125 | 1825 | 3103 | 3103-RT |
| 1-1/2" | RTC-150 | 1826 | 3104 | 3104-RT |
| 2" | RTC-200 | 1828 | 3105 | 3105-RT |
Connectors
| Trade size | CT | RACO | Bridgeport | Bridgeport raintight |
|---|---|---|---|---|
| 1/2" | RT-50 | 1802 | 3000 | 3000-RT |
| 3/4" | RT-75 | 1803 | 3001 | 3001-RT |
| 1" | RT-100 | 1804 | 3002 | 3002-RT |
| 1-1/4" | RT-125 | 1805 | 3003 | 3003-RT |
| 1-1/2" | RT-150 | 1806 | 3004 | 3004-RT |
| 2" | RT-200 | 1808 | 3005 | 3005-RT |
Cross references identify fittings of the same trade size, raceway type and fitting type. Ratings differ by manufacturer and series (for example, RACO couplings are listed concrete tight and Bridgeport RT fittings are listed raintight). Confirm the rating you need on the manufacturer's data sheet before substituting on a specified job.
Installation tips
- Cut the conduit square and ream the inside edge so the ring seats evenly and conductors are not damaged.
- Slide the nut and ring onto the conduit, then push the conduit fully into the fitting body until it bottoms out.
- Hand tighten the nut, then finish with a wrench. Do not use a pipe wrench on the body; it will distort the seat.
- On connectors, install the locknut inside the enclosure and tighten it until the fitting is snug and cannot rotate.
- Where the raceway is the equipment grounding conductor, verify continuity after installation.
Stock and pricing
All sizes from 1/2" through 2" are stocked. Same-day shipping on in-stock items. Distributors and contractors can request case and pallet pricing through our trade desk at 1 (307) 206-0534, or browse the full range in our Rigid and IMC Compression Fittings collection.
