Good one. I wasn't aware of that. I recall what we (in Rain Bird) called the ITT solenoid. It was large and a mustard yellow. I think the vendor was ITT, hence our internal name for it. Don't know if it had a spring. Then, we went to the green solenoid that is still used on some Golf Division rotors and our 3 inch BPE valve. I also don't know if it has a spring. (Products of other Product Managers.) Today, most and maybe all landscape valve solenoids at Rain Bird have springs. You guys like photos, so here is a cut away of a PE valve that used the green solenoid. When we went to the black solenoid, it became the PEB, for B series solenoid.