Bell Transfer MTB Cycling Helmet (Matte Black) Size:Medium (55-57)cm it means your "gap" is

it means your "gap" is greater than 2mm when chain is on big chainring (see video)

Commodity: Cleaning Accessories

plus a full complement of rack and fender braze-ons

20-inch wheel kids (aluminum)

Functions:

Bell Transfer MTB Cycling Helmet (Matte Black) Size:Medium (55-57)cm it means your "gap" isBorn from Bell's unrivaled heritage in motocross, the Transfer was created for everyday shredding. With Overbrow Ventilation to keep you cool and Quicksnap removable cheek pads for easy cleaning, this helmet is ready for ripping laps at the bike park or hitting your local DH race. Features Polycarbonate hard shell 9 vents 3 forehead vents Overbrow Ventilation Quicksnap cheek pads Specifications Recommended Use Downhill Gender Unisex Helmet Type Full