I've never owned or seen a bivy. Do they come with a sleeping bag built in? Or are they just a cover over your sleeping bag?

Tech Specs:

Material:

Epic fabric with 30D SilNylon floor 

Freestanding:

No 

Poles:

2 

Pole Material:

DAC Featherweight 

Stakes:

Yes 

Doors:

1 Top 

Clip/ Sleeve:

Internal sleeveless 

Floor Space:

20.4sq ft (1.9sq m) 

Interior Height:

25in (64cm) 

Vestibule Space:

N/A 

Seam Sealed:

No 

Bathtub Floor:

Yes 

Ventilation:

Bug netting over face 

Interior Storage:

No 

Packed Size:

5 x 7in (13 x 18cm) 

Weight:

1lb 10oz (734g) 

Recommended Use:

Ultralight bivy shelter for climbers, mountaineers, fast packers. 

Warranty:

Lifetime 

Country of Origin:

China