**Short answer:** "Same full scale" doesn't make an MFC a drop-in. Before an MKS unit replaces a Brooks unit (or the other way round), check seven things: **gas and calibration, full-scale range, fittings and length, I/O type and connector/pinout, supply voltage and power, response/settling, and seals**. MKS's own cross-reference chart only maps discontinued **MKS** models to current **MKS** models, and even there it warns that "the newer product is not a direct replacement" in some cases. No official MKS↔Brooks cross-reference is cited here. Treat any cross-brand swap as a **candidate to verify**.
Step 0: is your MFC already obsolete?
The MKS Flow Product Cross Reference Chart (examples, verbatim mapping):
| Discontinued MKS | MKS recommended replacement | Chart note |
|---|---|---|
| 1179A family (via GE50A datasheet) | GE50A | GE50A datasheet: its analog and digital I/O "can easily be used to replace those same I/O types of the 1179A" |
| 1159B, 1162B, 1749A, M100B | GE50A (elastomer-sealed) | — |
| 1160B, 1161B | GE50A | "Contact MKS Applications Engineering for Adapter Cable" |
| 1259C | GE50A | "…for Length Adapter" |
| 1759A | GE50A | Only "for flow rates up to 50 slm, N2 equivalent" |
| 1479A/B, 1480A, 1459C, 1462C | GM50A (metal-sealed) | 1461C also needs an adapter cable |
| 2159B, 2179A/B | GV50A (with shut-off valve) | — |
| 1661A, M200 | P4B | — |
The notes about adapter cables and length adapters are exactly the failure modes you get across brands too.
The checklist, with what the datasheets say
| Check | MKS GE50A | Brooks SLA5850 (SLA5800 Series) | What to verify |
|---|---|---|---|
| Full-scale range (N2 eq.) | 5–50,000 sccm | 0.003–50 slpm | Your FS and gas, not just N2 |
| Control range | 2–100 % FS | 1–100 % FS (100:1 from 1–50 slpm) | Lowest setpoint you actually run |
| Accuracy (cal gas) | ±1 % of reading 20–100 % FS. ±0.2 % FS for 2–20 % FS | ±0.9 % S.P. (20–100 % FS), ±0.18 % FS (<20 % FS), incl. cal-system uncertainty | Same definition and basis |
| Settling / response | <750 ms typical above 5 % FS (SEMI E17-0600) | <1 s (settling within ±2 % FS, 0–100 % step) | Recipe step timing. Definitions differ |
| Analog I/O | 0–5 VDC (9- or 15-pin D) or 4–20 mA (15-pin D) | 0–5 V, 1–5 V, 0–10 V, 0–20 mA, 4–20 mA (15-pin D) | Signal type **and** pin assignment |
| Supply (analog) | +15 to +24 VDC, <4 W | +13.5 to +27 Vdc. Up to 8 W (orifice >0.032″) | Tool PSU rail and current budget |
| Digital options | DeviceNet, RS485, Profibus, EtherCAT, PROFINET | RS485, Profibus, DeviceNet, EtherCAT, EtherNet/IP, PROFINET | Protocol **and** EDS/GSD/ESI file |
| Fittings | 4 VCR male, 4 VCO, 1/4″ compression, KF-16, C-seal, others. "Standard 3-inch footprint" | 1/4″ VCR, 3/8–1/2″ VCR, elastomer downport, others | Face-to-face length / footprint drawing |
| Seals | Viton std. Buna-N, Neoprene, EPDM, Kalrez options | Viton, Buna-N, Kalrez, Teflon/Kalrez, EPDM | Gas compatibility |
| Valve | NC or NO | NC, NO, meter | Same default state on power loss |
| Ambient | 10–50 °C | −14 to 65 °C | Enclosure temperature |
| Leak-by (closed valve) | <0.1 % FS (to 10K valve), <1.0 % FS (20K–50K) | <1 % FS standard | MKS: separate shut-off valve needed for zero flow |
Where drop-ins usually fail
1. **Connector pinout.** Both use 15-pin D-sub on analog versions, but don't assume the pins match. The current GE50A datasheet (10/21) lists only MKS 9-pin and 15-pin analog connector options (including "tied grounds" variants), with no Brooks-compatible pinout code. Compare pin-by-pin against each maker's installation manual before plugging in.
2. **Signal range.** A 0–5 V tool controller driving a 4–20 mA MFC (or a Brooks 1–5 V unit) gives wrong flow, or none.
3. **Gas calibration.** Both makers state accuracy on the *calibration gas*. Order the unit calibrated (or configured) for your process gas and FS. GE50A ordering uses a SEMI E52 gas code (e.g. 013 = N2) plus a 3-digit FS code (e.g. 502 = 5000 sccm). Don't apply a generic gas-correction factor from a third-party table to a substitute and assume the result is in spec. Ask the maker.
4. **Length and seals.** A different face-to-face length or seal type means a re-plumbed gas stick, not a swap. The MKS chart's "length adapter" note says the same.
5. **Digital network files and addressing.** DeviceNet MAC ID, Profibus station address and EtherCAT ESI must match the tool's configuration.
6. **Pressure differential.** GE50A needs 10–40 psid (10–5000 sccm range). SLA5850 needs a minimum of 5 psi. Check your supply pressure.
What to send in an RFQ (engineering + procurement)
- Current MFC: maker, full model / ordering code, serial-label photo
- Gas, full-scale flow, calibration gas required
- I/O: analog type (0–5 V / 4–20 mA…) or protocol, connector, any tool-specific pinout
- Fittings and footprint length; seal material; NC/NO
- Supply voltage available; ambient temperature
- Copy-exact only, or open to a cross-brand candidate for evaluation
- Quantity, need-by date, calibration certificate requirement
*MKS is a trademark of MKS Inc. Brooks is a trademark of Brooks Instrument. Names and model numbers are used for identification only. MST is not affiliated with or endorsed by these companies.*
Original OEM documents (links only)
1. MKS, "MKS Flow Products Cross Reference Chart" (web page). https://www.mks.com/n/mks-flow-product-cross-reference-chart
2. MKS, "GE50A Elastomer Sealed, Digital Mass Flow Controller" datasheet, GE50A_10/21. https://api.p1.mks.com/mam/celum/celum_assets/resources/GE50-DS.pdf
3. Brooks Instrument, "SLA5800 Series Elastomer Sealed, Digital, General Purpose Gas Mass Flow Controllers & Meters" datasheet, Data-Sheet-SLA5800-EN/2026-07. https://www.brooksinstrument.com/hubfs/Data-Sheet-SLA5800-EN.pdf
4. Brooks Instrument document library (SLA5800 Installation & Operation Manual and protocol supplements, for pinouts). https://sales.brooksinstrument.com/service-support/download-documents
Request a quote
Need a like-for-like MFC or a calibrated candidate for your gas? Post a [find-part request](/community/new?kind=part_request&mpn=GE50A) with the checklist fields, or send a [sourcing RFQ](/services/sourcing-rfq?sourcing_mode=supplier_match). MST replies in the thread or by email. MST does not claim stock of any model mentioned here; sourcing is done on request.
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