West System Mini Pumps 5:1 (300)


300 series – For 1.2L, 4.8L, 12L and 24L kits

5:1 Ratio

These pumps are calibrated to deliver the proper working ratio with one full pump stroke of resin for each one full pump stroke of hardener.



300 Mini Pumps are designed for convenient and accurate metering of Group A, B, and C WEST SYSTEM 105 Resin-based epoxy. The 300 Mini Pump Set Contains one resin pump and two hardener pumps. Pumps mount directly on the resin and hardener containers and eliminate the mess involved with measuring by weight or volume.

These pumps are calibrated to deliver the proper working ratio with one full pump stroke of resin for each one full pump stroke of hardener. 105/205-206 pumps deliver approximate 0.8 fl oz of resin/hardener with one full stroke of each pump. 105/207-209 pumps deliver approximately 0.9 fl oz of resin/hardener with one full stroke of each pump.

Made of durable polypropylene, the Mini Pumps give years of dependable service. Read and follow the priming, ratio verification and operating instructions that come with the pumps.

As packaged, the pumps are ready to install on the Group Size B containers. A package of extension tubes for Group Size A containers is included with the set. Group Size C extension tubes are included in the 105-C Resin and in the 207-SC or 209-SC packages.

Many WEST SYSTEM® Epoxy users take their new Mini Pumps out of the bag, mount them on the resin and hardener cans, and begin dispensing and mixing epoxy without ever having read the instructions. Most use them for years without a problem. Of those who do experience a problem, we’ve found that it most often could have been prevented by—you saw this coming—reading the instructions. The instructions offer simple steps that you can take to help assure that every batch of epoxy you apply to your project will cure properly and reach its maximum strength.

The ratio of each pair of pumps is controlled by the installation of a  clip, that limits the stroke (and volume) of one or both of the pumps. All pumps are carefully inspected during this operation and during packaging. But the final test of a pump’s performance can’t be made until it is actually pumping resin or hardener, a test we can’t perform and still keep the 300 Mini Pumps affordable. The ratio verification test described in the instructions confirms that both pumps are dispensing the correct volume and that the ratio of resin to hardener is within a critical narrow range.


Epoxy metering pumps ensure you’re using the correct ratio of resin to hardener, crucial to epoxy performance. Depending on the hardener you select, WEST SYSTEM Epoxy is mixed at a ratio of five parts resin to one part hardener, or three parts resin to one part hardener. At the proper mix ratio, the number of chemically reactive sites in the resin balances the number of reactive sites in the hardener. The resin molecules are larger than the hardener molecules, and have few reactive sites, hence the 5:1 or 3:1 ratio. When the mix is stirred thoroughly, the resin and hardener molecules react to develop full strength.

If the mix contains excess hardener, hardener molecules will remain unreacted in the cured epoxy, weakening it. They can also prevent subsequent paint coatings from setting up. NOTE: Never add extra hardener in an attempt to alter cure speed. This will only throw the resin-to-hardener ratio off, preventing the epoxy from reaching its full potential, and possibly even keeping it from hardening.

Many people epoxy in small batches, mixing several ounces at once. The most popular epoxy metering pumps are 300 Mini Pumps. They get the job done 95% of the time. For larger projects, you may need a larger pumping system such as the Model A Epoxy Metering Pump.

Epoxy Metering Pumps for Fast Dispensing

Our WEST SYSTEM Positive Displacement Pumps dispense epoxy faster than any pump we’ve ever offered. Positive Displacement Pumps work by trapping a fixed amount of resin and hardener then forcing (displacing) that trapped volume into the discharge pipe.  This offers improved epoxy pumping performance because changes in viscosity due to temperature change do not affect their performance.

Our epoxy metering pumps dispense epoxy at either a  3:1 ratio (for use with blush-free 207 Special Clear Hardener or 209 Extra Slow Hardener) and is easily identified with a red base. The 305 Positive Displacement Pump is calibrated for 5:1 ratio epoxies (with 205 Fast Hardener or 206 Slow Hardener) and has a blue base.

For more on mixing epoxy in large volumes (with or without epoxy metering pumps). read Big Batch Mixing Methods at Epoxyworks.


Now that you made the right decision and bought the pumps, here’s how to make the most of your purchase.

When you first install the pumps, check to make sure the resin pump is ready to use. Hold the white cap that screws onto the can and the clear plastic pump barrel and make sure they are screwed together snugly. You will also want to check on this from time to time.

Priming the pumps before the first use is simple but important; the instructions in the package explain how to do this. You will want to check the prime if the pumps been sitting for a long time, or when changing cans.

That’s right, when changing cans. No need to buy new pumps every time you buy new cans of epoxy. Store the pumps right on the cans and when you run out of WEST SYSTEM Epoxy you can move your pumps to the new cans of resin and hardener.

If the pumps have been sitting on the cans for a while they may develop a crust on the end of the spout. Hardener pumps particularly seem to do this. The crust is easily cleaned away: just break it off and wipe the spout. You can use warm water to clean the hardener pumps and acetone or denatured alcohol for the resin pump, if needed.

Use only full pump strokes and do not pull up on them; let them return on their own. Alternating one stroke of resin and one stroke of hardener eliminates the need to count strokes and reduces the time spent waiting for the pumps to return to the top of their stroke. Slow pump return can be an issue when using epoxy in cooler weather when the epoxy becomes “thicker” (actually, more viscous as our chemists would say). Try to keep your resin and hardener warm even if what you’re working on isn’t. Mix your epoxy indoors if you’re working at low temperatures in the garage. In the boatyard, an empty cooler and a shop light with an incandescent 15-watt bulb will keep your resin and hardener nice and warm.

Remember, warm epoxy will cure faster until it hits the cool/cold surface. Call and talk to one of our Technical Advisors about cold temperature bonding applications, or check our User Manual & Product Guide, visit westsystem.com, or see “Cold Weather Bonding” by Don Gutzmer in Epoxyworks 43.

Lastly, long-time WEST SYSTEM users may still have pumps with white tops (which we stopped selling back in 2002). The white-top pumps and the newer yellow top pumps are not compatible and should not be combined. But as long as your old white-top pumps are still delivering resin and hardener on ratio (verified by a simple pot-life test), they’re good. See, we told you Mini Pumps were reusable.—Excerpted from 300 Mini Pumps: To Buy or Not to Buy? by Terry Monville in Epoxyworks 49