Traffic Supply, Inc stocks the following 3M and Apex Raised Pavement Markers (RPM's):

Type A non reflective white dot.

Type AY non reflective yellow dot.

Type B two way white reflective RPM.

Type C one way white/one way red reflective RPM.

Type D two way yellow reflective RPM.

Type G one way white reflective RPM.

Type H one way yellow reflective RPM.

Type BB two way blue reflective hydrant RPM.

Type GG two way green reflective RPM.

Type RR two way red reflective RPM.

Apex manufacturers the traditional RPM, a hollow plastic shell with thin sheet glass bonded to a prismatic reflective surface on one or both sides, which is  filled with resin and has a sanded bonding surface.  These markers are more expensive than the 3M line, but remain in favor with many municipalities.  These markers are typically applied to the pavement with two part epoxy or hot bituminous rubber.

3M's 290 series raised pavement markers feature a solid plastic body with abrasion resistant polycarbonate reflectors.  Type D, G, H and BB 3M series 290 RPM's are also stocked with an aggressive factory applied peel-n-stick adhesive which eliminates the cost and mess of using epoxy. 

Information on the Apex line of pavement markers is available on their website.