Medical devices comprising a syringe barrel and a two-piece plunger rod are provided. According to one or more embodiments, the two-piece plunger rod includes a distal portion and proximal portion slidably mounted to the distal portion. The distal and proximal portions include a tab and plurality of grooves which engage to adjust the overall length of the plunger rod to a plurality of locked lengths. The locked lengths of the plunger rod permit varying amount of fluid to be expelled from the barrel.
