Side by side.

Specification	SD-510 SD-510 Quote
Width	1.132"
Height	0.625"
Flange	0.125"
Material	Rubber
Type	Sponge
Durometer	2A2 (sponge grade)
Colour	Black
Mount	Push On
Bulb position	Side
Core	SD-487 Spring Steel
Industries	Recreational Vehicles and Heavy Trucks

Spec sheets live on each part's page.