Are these Mylar? Product photos indicate other material...

If these are Mylar, they are the cheapest Mylar flips I've ever seen. They're so thin, they'll crack in no time. The ones I ordered are being sent back.

After putting coins in saflips, will they fit into slots of 20 pocket album pages?

The saflips are 2.5 x 2.5. Standard album page pockets are for 2x2 holders, so likely will not fit.

Are these acceptable for coin submissions to ngc / pcgs?

Yes. These will be acceptable to send your coins in to coin grading companies.

Can the flips scratch thick coins when you're putting them in? Since thick coins scrape against the inside more than thin coins.

Saflip brand Mylar flips by E.T. Kointainer are the standard in archival safe flips suitable for long-term protection. They contain no oils or other additives and will not corrode or cloud your coins like other flips can. They come packaged in poly bags of 50 flips to keep them free from contamination. Most of the double pocket coin flips today are made of vinyl, the common name of polyvinyl chloride (PVC). These PVC flips are available in both "soft" and "hard" versions and both types are dangerous for storing coins. The chemicals that can bleed out of the vinyl and the hydrogen chloride gas that the vinyl emits are corrosive to coins, causing sticky green slime, cloudy appearance and microscopic pitting of the coin's surfaces. This is why museums don't use vinyl of any kind, because museums know there is no such thing as safe vinyl. In 1979 E&T Kointainer Co. began researching an inert, museum quality double pocket coin flip. This research resulted in the development of a pure Mylar holder, the Saflip in 1980. Since then, collectors have had an alternative to the dangerous vinyl holders that ruined so many coins.Since 1980, millions of Saflips have been purchased and used by collectors, dealers and museums to safely store coins. In all those years, not a single coin has been damaged by these archivally safe coin flips. Saflips are manufactured under rigorous conditions to keep them uncontaminated by oil or machine dirt. Saflips are packaged in inert poly bags -- they are free of paper and cardboard dust that might cause spotting. Acid and sulfur free identification cards are available and can be inserted into one of the pockets. Saflips have been purchased by Harvard, Princeton, Cornell and James Madison Universities and Michigan University for use in their libraries and museums. Museums and universities use Saflips and you should too.