Precision Custom Rubber Molding
Tool Design - Production Design & Testing
High Quality Engineered Rubber Products
Over 60 Years Combined Experience

20 Years

Rubber compound development, evaluation, and improvement

28 Years

Casing plunger design/development, manufacturing, testing, evaluation, and field applications

60 + Years

Oilfield rubber and plastic molding industry including tool design, manufacturing processes, and product development

About Us

Lone Star Rubber Company was founded by Windel and Sherry Mayfield in 1979. Windel, a West Texas native, got his oilfield start on workover rigs. A graduate of Texas A&M, he has worked at Regal International, Oil States Rubber, and Gates Molded Products. Lone Star Rubber produces custom-designed and -manufactured rubber and plastic parts. In 1999 Windel and partners formed a separate entity, PAL Plungers, to produce a revolutionary new casing plunger. Derek Mayfield, son of Windel and Sherry, joined Lone Star in 2008. Derek is a 2001 graduate of Texas A&M.

Best Compound
Top Quality
Replacement Cups
Simply put - it's a better design


4½” 10.5# CASING

The Design

This high quality casing plunger sealing cup was designed to fit and perform well on a variety of plungers including most of the common tools having a 2 3/8” diameter body tube. These casing plungers are manufactured by Endurance Lift Solutions (formerly Multi Plunger Lift)Concoyle Oilfield Tools, and Swab-Rite Tool Corp, among others.

Field Tested

The rubber compound used in molding this cup was developed through years of evaluation in actual field tests on several different styles of casing plungers.

Extended Life

Cup life on these tools has proven to far exceed competitors’ cups. The extended life of the cup and its high quality compound formulation provide trouble free operation of the tool, yielding a reduced operating cost. A simple spacer change is all that is required to take advantage of this superior cup. Cup OD is designed to be used in 4 ½” 10.5# casing with other sizes available in the future.



Frequently Asked Questions

Yes. Our cups work on Swab-rite, Jet Star (by Multi Products), and Concoyle plungers. Our cup has an insert length of one inch which requires a change in spacer length. We can give you the necessary length or we can furnish the spacer if you like.

Our cup has been used on many Concoyle plungers with no problems on descent.


Most users report that our cups outlast the OEM cups by a significant amount. Cup life in all casing plunger wells is affected by casing condition, type of fluid being lifted, and amount of fluid lifted in each cycle.