Shop Chamberlain Garage Door Opener 8-ft Chain Rail Extension Kit in the Garage Door Opener Parts & Accessories department at Lowe's.com. The Chamberlain-8 ft Belt-Drive Extension Kit is compatible with Chamberlain Whisper Drive and Whisper Drive plus belt-drive garage door openers. Shop Chamberlain Garage Door Opener 8-ft Belt Rail Extension Kit in the Garage Door Opener Parts & Accessories department at Lowe's.com. This belt drive rail extension kit features a quick-install rail system. We design and engineer residential garage door openers, commercial door operators and gate entry systems. Genie Chain Drive 750 3/4 HPc Garage Door Opener w/Battery Backup - Heavy Duty Chain Drive - Oper… Fully compatible: the Chain Drive Rail Extension Kit for 8-ft high Garage Doors is required for reliable, everyday operation of Chamberlain®Â chain drive This Chamberlain® Extension Kit is needed for garage doors that are eight feet high and are compatible with Chamberlain® belt drive garage door openers. Chamberlain Group (CGI), the corporate parent company to LiftMaster, Chamberlain, Merlin and Grifco, is a global leader in access solutions and products. Read our story.