--- title: What Do the Letters and Numbers on Wiseco & JE Pistons Mean? description: Decode Wiseco and JE piston notations like “1,W” — learn what each number and letter means for fitment, compression, coating, and performance in motorsport builds. --- [Skip to content](https://info.speedingparts.eu/what-do-the-letters-and-numbers-on-wiseco-je-pistons-mean#main-content) [![Speeding\_Logo\_black\_Byline\_pp-2](https://info.speedingparts.eu/hs-fs/hubfs/Speeding_Logo_black_Byline_pp-2.png?width=200&height=60&name=Speeding_Logo_black_Byline_pp-2.png)](https://www.speedingparts.eu) Open main navigation Close main navigation How can we help you? - There are no suggestions because the search field is empty. 1. [Speeding Support](https://info.speedingparts.eu/?hsLang=en) 2. [Engine](https://info.speedingparts.eu/engine?hsLang=en) # What Do the Letters and Numbers on Wiseco & JE Pistons Mean? ## Decode Wiseco and JE piston notations like “1,W” — learn what each number and letter means for fitment, compression, coating, and performance in motorsport builds. ### What Do the Notations on Wiseco & JE Pistons Mean? ![](https://www.speedingparts.com/image/23607/wiseco-je-piston-foot-notes.jpg)     What do the notations on Wiseco and JE pistons mean? For example, when it says "**Foot note: 1,W**," what does that actually mean? **The various designations are listed in order below:**     #### 1 - Most wiseco pistons have offset pins. Pins must be offset same as OEM for quietest operation. ![](https://www.speedingparts.com/image/23619/piston-offset-pin-chart.jpg)     #### 2 - Due to a compression height that may protrude above the deck, it is recommended that a 1,00mm tick head gasket is used.     #### 4 - Utilizes extra deep valve pockets to expand the range of I-Vtec/Vanos with big/high lift cams and milled heads     #### 6 - These pistons have an oil ring groove that is lower than OE. Will not work with sleeves with access hole if the oil ring is not pinned in place     #### A - Rings need file fitment to the bore     #### B - Washers included     #### C - Stroker kit for B25 stroker crank     #### D - Weight reduction possible     #### E - With valve pockets unlike K557M series     #### F - FSR series (Forged side releaf) FSR (Forged Side Relief) skirts with a forged design have a shorter skirt width and shorter piston pins compared to traditional "full round" style pistons. The narrow skirt helps minimize contact with the cylinder wall, which causes friction / power loss. Shorter piston pins also reduce the overall weight.     #### G - Only with 2,5 Ltr conrods     #### H - Based on Volvo rod 23mm Ford OEM 21mm     #### I - Tuff skirt Coating JE Pistons     #### J - Mini Tritec engine     #### K - Compression ratio depends on cylinder head used     #### L - Pin 20mm - OEM 20,65mm (3/16)     #### M - Made to order (4pcs minimum)     #### N - Aluminum cylinders like Alusil, Lokasil, Silitec, DiASil, Mercosil, ALBOND, FRM, MMC, recommended to run sleeved bores / must sleeve block or Nicasil     #### O - VR6 cylinder sets from stock can be used     #### P - Piston guided rod required     #### Q - Oil squirter modification or removal required or use adequate spacers, please make sure to check rod to oil squirter clearance when relocating oil squirter     #### R - Full round skirt with or without full milled side relief     #### S - Asymmetrical FSR series FSR Series = Forged Skirt FSR (Forged Side Relief) skirts with a forged design have a shorter skirt width and shorter piston pins compared to traditional "full round" style pistons. The narrow skirt helps minimize contact with the cylinder wall, which causes friction / power loss. Shorter piston pins also reduce the overall weight.     #### T - Accepts Turbo and Nitrous     #### U - Head is the other way around on the Eclipse vs the later EVO's     #### V - Accepts Nitrous and E8     #### W - C/R calculated with OE head gasket     #### X - C/R calculated with 1,00mm head gasket     #### Y - 3D Undercrown milling included     #### Z - Alusil suited     #### PS - Perfect skirt coating JE Pistons     #### UL - Ultra series (Lateral Gas Ports, Accumulator Grooves, Skirt Coating, Ceramic Crown Coating, Upgraded Pins)     ### ▼ #### [Pistons](https://www.speedingparts.com/c/motor-tuning/motordelar/smidda-kolvar/) - [Hose and Fittings](https://info.speedingparts.eu/hose-and-fittings?hsLang=en) - [Engine](https://info.speedingparts.eu/engine?hsLang=en) - [Fuel System](https://info.speedingparts.eu/fuel-system?hsLang=en) - [Brake system](https://info.speedingparts.eu/brake-system?hsLang=en) - [Chassis](https://info.speedingparts.eu/chassis?hsLang=en) - [Powertrain](https://info.speedingparts.eu/powertrain?hsLang=en) - [Electrical](https://info.speedingparts.eu/electrical?hsLang=en) - [Turbo](https://info.speedingparts.eu/turbo?hsLang=en) [![Speeding\_Logo\_black\_Byline\_pp-2](https://info.speedingparts.eu/hs-fs/hubfs/Speeding_Logo_black_Byline_pp-2.png?width=200&height=60&name=Speeding_Logo_black_Byline_pp-2.png "Speeding_Logo_black_Byline_pp-2")](https://www.speedingparts.eu) Copyright © 2026, Speeding AB