Small bubble or large bubble
Small bubble, usually around 10mm, sits almost flat against a surface. That is what you want on anything with a face to protect: picture glass, mirrors, television and monitor screens, glazed ceramics, tiles, worktop appliances. Because it conforms, it spreads a knock across the whole panel rather than concentrating it on one point.
Large bubble, 20mm or more, is mostly air. Laid over a flat surface it makes contact in a widely spaced grid, which is exactly the wrong geometry for glass. Where it earns its place is filling the dead space around an awkward object: a lamp base, a vase, a kettle, a food mixer. Two turns of large bubble turns an odd shape into something roughly box shaped that will sit in a carton without moving.
If you are buying one roll, buy small bubble. Most houses never need the large.
Roll width
500mm is the useful width. Fold it over and you have a metre of coverage in one pass, which handles most framed pictures, a laptop, a shelf of ornaments. Narrower rolls, around 300mm, are handy for wrapping round things rather than over them, which is the job large bubble tends to be doing anyway.
What actually needs it
Less than you would guess. Run through a house and the genuine bubble wrap list is usually: framed pictures and mirrors, the television, a computer monitor, a few ornaments, the glass shelves out of a cabinet, a table lamp or two and anything with a ceramic glaze you would be upset to chip. Everything else is a paper job.
The common mistake is wrapping crockery in bubble wrap. It works, but it is several times the cost of paper, it takes up far more room in the box so you need more boxes, and it is no better. Plates on edge in crumpled paper is the method we use on every job.
How to use it
Bubbles facing in, flat side out. The bubbles form the cushion, the smooth face takes the tape and the abrasion. Never tape directly onto a painted, polished or veneered surface, and never onto a screen. Tape the wrap to itself.
For picture glass, put a strip of tape corner to corner across the glass first. If it does break, the tape holds the pieces together instead of letting them travel through the frame. Then wrap, and always carry and transport glass and framed pieces on edge rather than flat.
One thing to watch: do not leave bubble wrap in direct contact with a polished or high gloss surface for weeks in storage. In a warm store the polythene can mark the finish. Put a sheet of packing paper between the two.