
They are small and fit in a switch box if there are not too many wires. The nice thing is that you can still use the individual 3 position or even 4 position switches that you have. Many other solutions require the purchase of a second switch as a slave.

π BroadLink Smart Button: 3 Way Dimmer Switch Control with IFTTT and Alexa, Wireless Home Automation Hub Included
9 Review

Remotec ZRC-90US & BW8510US | Cert ID ZC10-15100007
9 Review

π GE myTouchSmart WiFi Smart Light Dimmer: Works with Alexa & Google Assistant, No Hub Required
9 Review

Moes WiFi Smart IR Remote Controller: Universal Infrared Blaster for Smart Home, Alexa and Google Home Compatible - AC, TV, DVD, CD, AUD, SAT Control, No Hub Required
9 Review

π‘ Electronic FL Ballast ICN-4P32-N (Formerly ICN-4P32-SC) for 3-4 F32T8 F40T8 F17T8 Lamps, 120V/277V Compatibility
5 Review

Wireless Electronic Ballast Interface Certified
8 Review

π‘ Hydrofarm Quantum QT400 Dimmable Ballast for 400W Grow Lights
5 Review

Robertson Worldwide ISL432T8HEMV AH 3P20160 120-277V 50-60Hz High Power Factor 4 F32T8 Linear Lamp Fluorescent eBallast
6 Review