Gems Sensors have piston flow switches available in plastic and alloy designs. Plastic flow switches include the noryl-based FS-3 fixed for liquids up to 1.0 GPM and gasses up to 12 CFM, the polypropylene based FS-380P for liquids up to 2.0 GPM and the polypropylene FS-150 for liquids up to 5 GPM. Alloy switches include the stainless steel/brass FS-927 for flows up to 1.5 GPM, the stainless/brass FS-380 for flows up to 2.0 GPM and the brass OR stainless steel FS-10798 for flows up to 20 GPM. Many of the flow switches can be used for gas applications as well.

Grainger Industrial has a variety of 3/8" liquid flow piston switches with flow rates from .15 to .50 GPM, and pressure ratings between 115 and 125 PSI. Polypropylene housed sensors can test temperatures up to 212F, and have a contact rating of 10VA. Brass housed sensors can test temperatures between -20F and 275F, and have a contact rating of 20VA.

Banna Electronics has a range of magnetic flow switches for both liquid and gas applications, and are designed for industrial, machinery, air, cooling and HVAC systems. All models feature spring-supported magnetic pistons, and are available in stainless steel and anodic alumina.

Dwyer Instruments Series 4 PPS piston flow switch has fixed set points from 0.1 to 1.5 GPM and features a fully molded plastic construction for added resilience. The switch has a PPS R4 housing, 316S spring and a fluoroelastomer for durable, leak free operation. Inlet/outlet connectors are 9/16"-18 UNF-2B and have optional barbed adapters for 1/8", 1/4" and 1/2" systems.

Innovative Solutions F002 is a piston-based flow switch available in brass or 316 stainless steel, rated up to 1000 PSIG. Standard connectors are 1/4" (with a 1/2" electrical conduit connection), and are designed to measure liquid water flows from 0.2 to 1.5 GPM, and can be modified to read fluid viscosities up to 550 SSU.

The series 2100 polysulfone flow switches are available in 1/8" and 1/4" sizes, FDA approved, and are designed for HVAC equipment, OEM components and in conjunction with machine tools. It can operate with pressures up to 250 PSI, with a low-flow point set to 1 cc per minute.

Digi-Key has three reed-based Cynergy flow switches, available in 15 and 22mm diameters. All of the flow switches are designed for liquid systems, and are lead-free and RoHS compliant.

Sika's VM100 flow switch is designed for marine systems, and feature an inline installation, wide set point range, a variety of fitting positions and a reed contact output. Though designed primarily for water, the switch is also available for petroleum based systems. 

Orange Research flow switches are compact, and designed to measure from 0.1 to 1.5 GPM with a maximum pressure of 1000 PSIG. Orange flow switches are available in brass and stainless steel.